A cargo vessel in the Strait of Hormuz has been hit and damaged by a projectile — hours after Iran ordered four ships in the vital shipping lane to turn back.

The vessel sustained damage to the bridge after being struck on the starboard side around 10 a.m. EST Thursday, according to UK Maritime Trade Operations, which issued a warning to other ships of an attack in the Strait.

It happened the same day at least four tankers were turned back by Iran while trying to pass through the strait after being stuck in the Persian Gulf for more than 100 days, the Financial Times reported.

It is not clear whether there is any wider attempt to close or restrict traffic in Hormuz, through which 20% of the world’s oil supply flows.