The United States and Britain have carried out strikes on Houthi-linked targets in Yemen, four US officials told Reuters on Thursday, for the first time since they began threatening international shipping in the Red Sea late last year.

The Houthis, who control much of Yemen, attacked Red Sea shipping lanes to show their “support for Palestine and the Gaza Strip” following Israeli bombings. The attacks disrupted international trade on a key route between Europe and Asia, which accounts for about 15% of global shipping trade.

These are believed to be the first US strikes against the Houthis in Yemen since 2016.

The officials, speaking on condition of anonymity, said an official statement detailing the attacks was expected soon.

Earlier on Thursday, the Houthi leader said any US attack on the group would not go unanswered.

The Houthis, who captured much of Yemen in a civil war, have vowed to attack ships linked to Israel or heading to Israeli ports. However, many of the ships attacked had nothing to do with Israel.

The US military said on Thursday that the Houthis fired an anti-ship ballistic missile into international shipping lanes in the Gulf of Aden, the group’s 27th attack since November 19.