Houthi rebels in Yemen have vowed to continue attacks in the Red and Arabian seas after a suspected US attack killed at least 68 people.

The Houthi militia, which is backed by Iran, said the attack was an American strike. The U.S. Defense Department said it was assessing the claims and took them seriously.

Yemen’s Houthi rebels on Monday alleged a US airstrike hit a prison holding African migrants, killing at least 68 people and wounding 47 others. The US military had no immediate comment.