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South China Sea: PRC maritime enforcement near Taiwan and claimants’ build-outs keep tensions high

Time window: Last 7 days · Audience: General analyst · Type: Situation report · DTG: 2026-06-30 10:12Z · Overall confidence: MEDIUM

BLUF

PRC state vessels and agencies acted in and around Taiwan’s eastern waters and near Taiping Island in June, drawing public US censure. In the Spratlys, Manila’s new coast guard base on Thitu and Vietnamese expansion across 21 occupied features keep maritime frictions elevated and interaction risks with US and allied operations in play.

Executive summary

Taiwan’s foreign ministry and the American Institute in Taiwan publicly flagged PRC activity in Taiwan’s eastern waters on 24 June, after PRC government ships operated in those waters and around Taiping Island earlier in June. Beijing has asserted jurisdiction and organised maritime “law enforcement” actions in the area, while US statements rejected interference with freedom of navigation and pressed Beijing to halt pressure on Taiwan. In the Spratlys, the Philippines opened a major coast guard district base on Thitu Island on 10 April to bolster presence, a think tank reports Vietnam has expanded construction across 21 features it occupies, and PRC research-vessel activity has increased inside the Philippine exclusive economic zone alongside continued reclamation and militarisation on contested features. US and partner freedom of navigation operations continue, sustaining routine interaction risks. The stakes remain high given the scale of trade transiting the South China Sea and the assessed strategic impact of PRC maritime expansion on trade flows and military operations.

Change from previous assessment

New public statements this week from Taiwan’s foreign ministry and the American Institute in Taiwan detailed PRC activity east of Taiwan and around Taiping Island, updating the prior assessment that noted no corroborated new at-sea incidents in the window. The brief now adds a judgment on likely short-term persistence of PRC enforcement activity near Taiwan and incorporates recent context on Manila’s Thitu base and Vietnamese expansion in the Spratlys. Confidence on PRC activity near Taiwan is raised relative to the prior brief due to multiple corroborating official statements. Initial assessment of ASEAN code-of-conduct prospects under Manila’s chairmanship is added with low confidence.

Key judgments

1. PRC state maritime activity in and around Taiwan’s eastern waters and the vicinity of Taiping Island very likely intensified in June 2026 and will persist into early July, reflected in Beijing’s asserted jurisdiction and organised “law enforcement” actions and in US public censure. (Confidence: medium · ASSESSED)

• I&W: Further Chinese Ministry of Transport or maritime authority notices announcing special maritime law enforcement actions east of Taiwan. (0-14 days)
• I&W: No AIT/Taiwan MOFA statements and no observable CCG or MoT asset transits east of Taiwan on AIS for a continuous two-week period. (0-14 days)

2. Maritime frictions in the Spratly Islands are likely to remain elevated through the next quarter as Manila operationalises its Thitu Island coast guard base, Vietnam advances construction on 21 occupied features, and PRC vessels and infrastructure activity continue inside and around the Philippine EEZ. (Confidence: medium · ASSESSED)

• I&W: Philippine Coast Guard releases or imagery showing increased patrol sorties or facility activation from Thitu Island. (1-3 months)
• I&W: Commercial AIS or open imagery showing Chinese research vessels or engineering platforms operating within the Philippine EEZ near Spratly features. (1-3 months)

3. US and partner naval and air operations are likely to continue across the South China Sea and adjacent waters, keeping interaction risks with PLA units in the spotlight. (Confidence: medium · ASSESSED)

• I&W: Public announcements of new US or allied freedom of navigation operations or overflights in the South China Sea. (1-3 months)
• I&W: A sustained 60-day hiatus in publicised US or allied operations in contested South China Sea waters. (1-3 months)

4. There is a roughly even chance that Manila will try to balance deterrence with diplomacy during its ASEAN chairmanship, using its new Thitu outpost while pursuing a code-of-conduct push and deeper economic ties, but tangible de-escalation remains uncertain. (Confidence: low · ASSESSED)

• I&W: ASEAN schedules a working-level South China Sea code-of-conduct session chaired by the Philippines, with Manila communiques highlighting progress. (1-3 months)
• I&W: An uptick in reported PCG, CCG run-ins around Philippine-held features that crowds out diplomatic engagement in official communiques. (1-3 months)

Outlook & scenarios

Baseline: Grey-zone contest continues without open conflict (60%)

PRC coast guard and maritime agencies sustain presence east of Taiwan and around Taiping Island, while in the Spratlys Manila beds in its Thitu base and Vietnam continues work across 21 occupied features. PRC research vessels operate inside the Philippine EEZ as reclamation and militarisation endure, and US and partner FONOPs continue. Public signalling and operational friction persist but remain managed.

Escalatory flashpoint near Philippine-held features (30%)

A tactical confrontation near Thitu or along resupply routes to Philippine outposts triggers collisions or equipment damage, prompting sharp diplomatic exchanges and proximate force build-ups. PRC maritime militias and coast guard intensify presence, Vietnam accelerates fortification works, and US and partner patrols expand monitoring, increasing miscalculation risk.

Diplomatic opening with limited de-escalation signals (25%)

As ASEAN chair, Manila convenes working-level code-of-conduct discussions and emphasises economic engagement alongside security posture. Incidents continue at a lower tempo as parties test confidence-building measures, yet construction and patrol patterns remain largely unchanged pending any formal agreements.

Recommendations

1. Monitor Chinese Ministry of Transport and provincial maritime authority notices for references to special maritime law enforcement actions east of Taiwan, and correlate with AIS tracks of CCG and MoT assets.
2. Build a standing watchlist of Chinese research vessels operating inside the Philippine EEZ and automate alerts on AIS reappearances near Spratly features.
3. Task weekly open imagery collections to a feature-by-feature deck for Vietnam’s 21 occupied Spratly features to track dredging, shoreline changes and new structures.
4. Engage Philippine Coast Guard contacts for routine updates on the Thitu Island base activation timeline, patrol sortie rates and logistics footprint to gauge sustained presence.
5. Maintain a rolling log of US and allied freedom of navigation operations and overflights in the South China Sea to map interaction hotspots with PLA units.
6. Prepare a trade-exposure brief quantifying flows through the South China Sea and China’s reliance on these routes to inform escalation-risk assessments tied to maritime disruptions.

Confidence & uncertainty

Overall confidence is medium. Multiple official statements from Taiwan’s foreign ministry and the American Institute in Taiwan, together with reporting on PRC-organised maritime enforcement actions, corroborate recent activity east of Taiwan. Assessments of continued friction in the Spratlys and ongoing US and partner operations are grounded in credible think tank reporting and documented patterns but rely partly on analytic inference for forward-looking elements. Some sources are analytical rather than primary, and granular operational data is limited, creating uncertainty about tempo and intent.

Alternative analysis (red cell)

The reporting documents episodic June incidents, infrastructure expansion, and historical FON patterns, but lacks continuous operational indicators, tasking orders, or high-frequency incident data to support strong forecasts of sustained PRC intensification or guaranteed elevated Spratly frictions. A sober alternative estimate is that increased capability and intermittent actions raise the risk of incidents, but near-term outcomes hinge on immediate operational decisions by Beijing, Manila, and external navies and therefore remain materially uncertain.

Intelligence gaps

• [EEI 1.1 · PARTIAL] Number, class, and position (time-stamped) of Chinese Coast Guard (CCG), People’s Armed Forces Maritime Militia (PAFMM), and other PRC paramilitary/auxiliary vessels inside Philippine-claimed EEZ or within 12 nautical miles of Philippine-occupied features (e.g., Scarborough Shoal, Second Thomas/Ayungin Shoal, and other named features). Recommended collection: maritime/AIS
• [EEI 1.2 · PARTIAL] Observed maneuvers or posture indicating hostile action: vessel-to-vessel blocking/contact, use of water cannons, boarding attempts, formation maneuvers to interdict Philippine vessels, or sustained stationing near Philippine resupply/relief routes. Recommended collection: imagery/satellite
• [EEI 1.3 · PARTIAL] Incidents of Philippine vessels (coast guard, navy, supply boats, civilian fishing vessels) being ordered to alter course, detained, chased, or physically impeded — with time, location, involved units, and damage/injuries if any. Recommended collection: open-source/official statements
• [EEI 1.4 · UNCOVERED] Abrupt changes to vessel identification behavior: AIS transponder deactivations, spoofing, or mismatches between flagged identity and observed equipment/markings among PRC maritime law-enforcement or militia vessels operating near Philippine claims. Recommended collection: maritime/AIS
• [EEI 2.1 · UNCOVERED] Issued directives, patrol orders, or internal guidance from PRC Central Military Commission, PLAN, CCG, or provincial maritime authorities that specify objectives, geographic limits, patrol tempos, or escalation thresholds for operations near Philippine-claimed features. Recommended collection: signals/communications
• [EEI 2.2 · UNCOVERED] Public declarations, maritime notices, or newly published 'maritime safety' or exclusion zones, with effective dates and coordinates, issued by Chinese authorities that could be used to justify interdiction or exclusion of Philippine activity. Recommended collection: open-source/official statements
• [EEI 2.3 · UNCOVERED] Evidence of mobilization orders, tasking lists, or logistics planning for Maritime Militia units (vessel requisitions, local fisheries bureau instructions, fuel/resupply manifests) indicating intent to employ militia alongside CCG/PLAN assets. Recommended collection: HUMINT/defense
• [EEI 3.2 · UNCOVERED] Air component activity: number and frequency of Philippine air patrol sorties, maritime domain awareness flights, and air-to-surface or maritime strike assets placed on alert or redeployed toward contested areas. Recommended collection: imagery/satellite
• [EEI 3.4 · UNCOVERED] Changes to Philippine rules of engagement, emergency law measures, mobilization orders, or civil advisories (evacuations, fishing bans) that alter civilian or military behavior in contested maritime zones. Recommended collection: open-source/official statements

Cited sources

[1] Ministry of Foreign Affairs, Taiwan · 外交部感謝美方就中國侵擾我國東部海域之行動表達關切 (A) · sha256:3ff7770a7e66 [2] 壹蘋新聞網 · 中國海警頻侵擾　AIT：加劇緊張破壞穩定｜壹蘋新聞網 (B) · sha256:0ebf8d38f990 [3] Government of the Philippines · Philippine Coast Guard (A) · sha256:3cfd1efc2d3b [4] acleddata.com · Q&A: As South China Sea confrontations ramp up, what’s the risk of open conflict? (C) · sha256:7916ad9f9999 [5] media.defense.gov · [PDF] Confronting China's Maritime Expansion in the South China Sea (B) · sha256:26451c326ac7 [6] Wikipedia · Territorial disputes in the South China Sea (F) · sha256:1d5bd5a3150d [7] Wikipedia · Fourth Taiwan Strait Crisis (B) · sha256:36ef98bf8e33 [8] 163.com · 菲律宾专家质疑中国咄咄逼人，称仁爱礁停留24年为证 (B) · sha256:d8fbded937a5 [9] UK Government · Philippines moves forward as CPTPP parties begin accession talks (A) · sha256:e8f460a2affc

Source content hashes were computed at collection time; the cited text is preserved unmodified for the life of this product.

Red cell review: PARTIAL DISSENT

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