Iran escalates attacks in Strait of Hormuz as tankers test U.S. blockade

April 22, 2026

(Bloomberg) — Iran intensified pressure on shipping in the Strait of Hormuz, with gunboats firing on commercial vessels while its own oil tankers moved beyond the chokepoint, testing a U.S.-enforced blockade.

The UK Maritime Trade Operations (UKMTO) said a cargo ship and a container vessel came under fire in the waterway, with one sustaining significant damage to its bridge. Iranian state media later reported that two ships had been seized and brought ashore for inspection.

At the same time, data from analytics firm Vortexa showed two Iranian very large crude carriers (VLCCs), Hero II and Hedy, entering the Arabian Sea after departing the Gulf. The vessels, capable of carrying up to 4 MMbbl of oil combined, signal Tehran’s efforts to maintain exports despite U.S. restrictions.

The incidents underscore the fragile security environment in Hormuz, which handles roughly one-fifth of global oil flows. The latest escalation comes as U.S.-Iran negotiations remain stalled and Washington maintains a naval blockade aimed at curbing Iranian shipments.

Since tightening enforcement earlier this month, the U.S. has seized or turned back multiple vessels, expanding its reach beyond the Gulf. However, tracking data indicates Iranian exports have continued, with dozens of tankers navigating the region — often with transponders switched off to avoid detection.

The conflict has already removed significant volumes from global markets, contributing to ongoing volatility in oil supply chains. Around 800 vessels remain stranded in the Persian Gulf, according to maritime officials, as shipping companies weigh risks tied to renewed attacks and uncertain passage conditions.

While a ceasefire has been extended, the continued blockade and sporadic incidents highlight the difficulty of restoring normal transit through one of the world’s most critical energy corridors.

Map of the Strait of Hormuz. Source: Global Energy Infrastructure.