Commercial ships still sailing through the Red Sea are broadcasting messages about their nationality and even religion on their public tracking systems to avoid being targeted by Yemen's Houthis after deadly attacks this week by the militia.

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.

At least two people were killed in the attack, the Ukrainian interior minister has said.