The United States on Wednesday added the Iranian-backed Houthi rebels in Yemen to its list of terrorist organizations, as the fighters targeted their second American-operated vessel this week in the Red Sea region and the US military launched fresh strikes.

Attacks by the militia on ships since November have disrupted trade between Asian and European ports and raised alarm among major powers amid an escalating conflict between Israel and the Hamas militant group in Gaza. The Houthi militia claims to be in solidarity with the Palestinians and has threatened to resume attacks on American and British vessels in response to US strikes on their positions.

The Houthi movement claimed on Wednesday that its missiles had hit the American-flagged bulk carrier Genco Picardy, a shipping operator said in a statement. The vessel was struck by a missile while passing through the Persian Gulf with a load of phosphate rock, the statement said.

Genco said the crew was unharmed and the ship suffered minimal damage to its corridor and was on its way out of the area. hours later, the US military announced that its forces had hit 14 Houthi missiles that posed an immediate threat to commercial ships and US naval vessels in the area.

The Houthi-controlled Saba news agency reported that US and British strikes had targeted several areas in Yemen, and a spokesman for the group said the group would continue its attacks.

“The naval forces will not hesitate to target all sources of threat in the Red and Arabian Sea within the legitimate right to defend Yemen and to continue supporting the oppressed Palestinian people,” the group’s military spokesperson Yahya Sarea said in a statement.

On Monday, Houthi powers struck the U.S.- possessed and worked dry mass boat Gibraltar Bird with an enemy of boat long-range rocket. There were no reports of significant damage or injuries.