DUBAI, United Arab Emirates (AP) — A Liberian-flagged cargo ship caught fire in the Red Sea on Friday after being hit by a projectile launched from rebel-controlled Yemen, a U.S. defense official said.

The attack on the Al Jasrah further escalates a campaign by Yemen’s Iranian-backed Houthi rebels, who have claimed responsibility for a series of missile assaults in recent days just missing shipping in the Red Sea and its strategic Bab el-Mandeb Strait.

The U.S. official spoke on condition of anonymity to discuss intelligence matters. The Houthis did not immediately claim responsibility for the assault.

The Al Jasrah is operated by German-based shipper Hapag Lloyd, which declined to immediately comment about the attack. It wasn’t immediately clear if any of the crew on board the vessel had been hurt in the attack, which may have come from either a drone or a missile.