A tanker sailing in the Persian Gulf off northern Qatar was struck by several projectiles on Wednesday, and people aboard were hurt or killed, according to UK Maritime Trade Operations, the Royal Navy office that tracks threats to commercial shipping in the region.

In a short warning, UKMTO said the ship's crew reported the strike at about 1900 UTC, which was noon in California, roughly 51 nautical miles (about 94 kilometers) north of the Qatari town of Madinat ash Shamal. The agency said casualties had been reported but gave no number and did not say whether they were injuries or deaths. Authorities are investigating, and other ships were told to move through the area with caution and report anything suspicious.

What isn't known yet

The tanker has not been named. The Maritime Executive noted that UKMTO typically leaves vessel names out of its first reports, and AFP, in a report carried by Gulf News, said the agency did not say where the ship came from. Argus Media reported that no group had claimed responsibility and that the nationalities of the crew had not been released.

Why the location matters

Most recent attacks on shipping tied to the U.S. conflict with Iran have clustered around the Strait of Hormuz. This one happened much deeper inside the Gulf. Argus said Madinat ash Shamal sits about 100 kilometers north of Doha and about 54 kilometers from Ras Laffan, Qatar's major energy hub. The Maritime Executive called it the first reported tanker attack in the western half of the Gulf in weeks, and said that while U.S. aircraft have been guarding a narrow corridor near Hormuz, American forces have little presence farther west, leaving tankers off Iraq, Kuwait, Saudi Arabia, Bahrain and Qatar more exposed.

Martin Kelly, a former head of intelligence at the security firm EOS Risk Group, wrote on social media that it was the first time since Sept. 9 that Iran had struck a ship in the Gulf away from the strait, Argus reported.

The strike comes a day after the Panama-flagged tanker On Peace was attacked off Oman while transiting Hormuz, and Argus counted five attacks on vessels along Oman's coast since Oct. 3.

It is not the first time the waters off Qatar have been hit. On April 1, Qatar's defense ministry said an Iranian cruise missile struck the tanker Aqua 1, which was chartered to QatarEnergy, about 17 nautical miles north of Ras Laffan. No one was hurt in that attack, Reuters reported.