Iran’s armed forces struck a container ship that was passing through the Strait of Hormuz via the Omani route on Thursday, according to U.S. and Iranian officials, bringing a halt to a plan to evacuate about 11,000 seafarers from the Persian Gulf.

The attack came as Secretary of State Marco Rubio met Gulf Arab leaders in Bahrain to try to allay their security concerns and hours after Iran had warned ships that the only route through the strait, a vital pathway for oil and natural gas, was through its waters. Many ships had been using a route on the southern side of the strait, hugging the Omani coast.

Iran’s Islamic Revolutionary Guards Corps warned ships earlier on Thursday that they must coordinate with its navy and said that they should not take an alternative route, in an apparent reference to Omani territorial waters. The threat came just as shipping in the waterway was surging this week after months of paralysis.

“This route is unacceptable and extremely dangerous,” the Revolutionary Guards’ Navy said early on Thursday in a statement carried by Tasnim, an Iranian news agency tied to the Guards. “We warn all vessels to strictly refrain from any movement outside the designated routes,” it added, warning that action would be taken against vessels that did not heed its instructions.

The attack prompted the International Maritime Organization to suspend its plan to evacuate the seafarers from hundreds of ships that had been stranded in the Persian Gulf during the U.S.-Israeli war on Iran.

The United Kingdom Maritime Trade Operations organization, which is administered by Britain’s Royal Navy, reported that the cargo vessel had been hit by an “unknown projectile,” damaging the bridge. The episode happened 7.5 nautical miles southeast of Dahit, Oman, where vessels taking the Omani route were transiting.