A small boat mined a tanker in the Strait of Hormuz.

A small boat attached two limpet mines to the hull of a tanker in the Strait of Hormuz, starting a fire in the engine room and temporarily disabling the vessel, maritime sources told Reuters on Friday. The tanker was the Panama-flagged Louise 1. The sources called it the first successful use of such explosives in the waterway since the United States went to war with Iran in February. Greece-based Marisks said Friday: “The apparent ability of a small craft to approach a transiting tanker, deploy explosive devices and withdraw presents a significant security concern, particularly in the Strait’s congested shipping lanes.”

In a separate Reuters dispatch, Iran’s Revolutionary Guards Navy said four oil tankers had caught fire in the strait while using what it called unauthorized routes. Reuters could not immediately verify that statement. The United Kingdom Maritime Trade Operations agency said, separately, that a crude tanker was struck by an unknown projectile while completing an outbound transit, and earlier that a vessel was hit on its port side about 40 nautical miles south of Lavan Island, starting a fire. The crew were reported safe, and there was no reported environmental impact. Those reports are not one count, and this desk is not adding them to the Louise 1. Iran also said it downed an American MQM-170 drone over Qeshm. Reuters could not verify that, and there was no immediate American reaction. Iran said it destroyed an unmanned American vessel. Central Command said: “All U.S. military unmanned surface vessels in the Middle East are accounted for, including a squadron of advanced sea drones on patrol in the Strait of Hormuz.”

The apparent ability of a small craft to approach a transiting tanker, deploy explosive devices and withdraw presents a significant security concern.

The photograph is Oct. 23, vessels in the strait seen from Musandam, Oman. Reuters made it. It is not the Louise 1. No crew is named.