Iran declares Strait of Hormuz closed and warns ships will be targeted

IRGC Declares Strait of Hormuz Closed as US Naval Blockade Persists

IRGC declares the Strait of Hormuz closed amid a US naval blockade; attacks on commercial ships, stalled talks and rising oil volatility heighten tensions.

Iran’s Islamic Revolutionary Guard Corps (IRGC) announced on April 18, 2026 that the Strait of Hormuz is closed and that any vessel attempting to transit will be targeted, sharply reversing an earlier, short-lived reopening of the vital waterway. The declaration came after Tehran accused the United States of imposing a naval blockade on Iranian ports and vessels, a move Iranian officials say violates the terms of the ongoing ceasefire talks tied to the US–Israel conflict. International shipping, diplomatic channels and energy markets reacted immediately to the escalation as negotiators sought to salvage a deal before the ceasefire’s scheduled expiry on Wednesday, April 22, 2026.

IRGC Declares Strait of Hormuz Closed

The IRGC navy statement, carried by Iran’s Student News Agency, warned that ships leaving anchorage in the Persian Gulf or Sea of Oman and approaching the Strait of Hormuz would be considered as cooperating with the enemy and “will be targeted.” The announcement framed the closure as conditional, saying the strait would remain blocked until the United States lifted what Tehran described as a naval blockade on Iranian vessels and ports.

The move represented a dramatic reversal less than 24 hours after Iran briefly reopened the strait, a step that had been hailed by some international actors as a possible confidence-building measure. Tehran’s reassertion of control signals a hardening of posture amid continuing diplomatic uncertainty.

US Maintains Naval Blockade and Issues Warnings

The United States has maintained that its naval presence in the region is intended to secure freedom of navigation and deter threats to commercial shipping, while President Donald Trump warned that Iran could not “blackmail” Washington by attempting to close the waterway. Mr. Trump said the blockade would “remain in full force” and cautioned that the United States would reconsider the ceasefire arrangements if a negotiated settlement was not concluded prior to the ceasefire’s end.

US officials have argued the measures respond to regional security threats, but Tehran views the American actions as a direct violation of ceasefire understandings and an unacceptable infringement on Iranian maritime rights. The diplomatic impasse has added urgency to last-minute talks between Tehran and Washington.

Commercial Ships Targeted After Early Reopening

Reports from United Kingdom Maritime Trade Operations (UKMTO) and regional authorities said Iranian gunboats fired on at least two commercial vessels on April 18, 2026, and that merchant ships in the area received radio warnings from the IRGC navy. India’s Ministry of External Affairs reported that two Indian-flagged ships were involved in a shooting incident in the strait, underscoring the multinational risks to commercial operators.

More than a dozen commercial ships managed to transit during the brief reopening on Friday, but the IRGC’s later reversal left ships and operators facing heightened threats and operational uncertainty. Maritime insurance rates and rerouting options were immediately expected to be reassessed by shipping companies.

Negotiators Offer Contradictory Signals

The developments exposed conflicting messages from Iranian officials and negotiators. Mohammad Bagher Ghalibaf, Iran’s parliament speaker and a senior negotiator in talks with Washington, asserted on television that “the Strait of Hormuz is under the control of the Islamic Republic” and described the American blockade as “a clumsy and ignorant decision.” By contrast, Iranian Foreign Minister Abbas Araghchi had said on Friday that the waterway was “completely open for all commercial vessels,” a statement that briefly eased market fears before the IRGC’s closure.

Observers say the mixed signals reflect internal debate in Tehran over how best to leverage control of the strait in negotiations, and how to respond to perceived US pressure. The rapid shift has complicated efforts by mediators to secure a durable agreement before the ceasefire deadline.

Regional Reactions and Diplomatic Alarm

Regional capitals and trading partners reacted with alarm to the renewed threat to one of the world’s most important maritime choke points. International shipping organizations and affected states called for calm and urged all parties to respect freedom of navigation under international law. Analysts noted that the return to confrontational tactics could undermine fragile diplomatic progress in the weeks leading to the ceasefire’s expiry.

Al Jazeera correspondents characterized the standoff as a return to “two competing blockades,” with Tehran using the Strait of Hormuz as a bargaining lever while the US maintains naval pressure. Governments with commercial vessels in the region signalled readiness to engage diplomatically while seeking immediate safeguards for their ships and crews.

Oil Markets and Shipping Disruption

Markets reacted swiftly to the uncertainty. Oil prices fell initially after Friday’s statement that the strait was open, but the IRGC’s decision to close the waterway and reports of gunboat attacks reversed that calm and injected volatility back into energy markets. Traders and analysts warned of potential supply disruptions if the closure persisted or if shipping routes were forced to detour around longer, costlier passages.

Shipping firms faced immediate operational challenges with vessel scheduling, crew safety and insurance implications. Even short-term disruptions in the Strait of Hormuz, through which a significant share of global seaborne oil transits, can ripple through global supply chains and refine shipping logistics across the Gulf and beyond.

Diplomats and military officials from affected countries continue to monitor developments closely. With the ceasefire due to expire on Wednesday, April 22, 2026, stakeholders face a narrow window to defuse the standoff and restore unimpeded commercial navigation in the Strait of Hormuz.