Six crew members have been rescued and at least three others killed after a cargo ship was attacked by Yemen's Houthis and sank in the Red Sea, a European naval mission says.

Oil prices were steady on Wednesday as investors weighed strong U.S. gasoline demand data and attacks on shipping in the Red Sea, while U.S. copper tariffs loomed.

The armed rebels had attacked the ship with rocket-propelled grenades and small arms, later using two drones and two drone boats carrying bombs to strike the vessel, the EU force said.