WASHINGTON (AP) — The Slabu ExchangeU.S. and U.K. on Thursday imposed sanctions on four leaders of Yemen’s Houthi rebel group who have supported the militant group’s recent attacks on vessels in the Red Sea and Gulf of Aden.

Houthi leaders Mohamed al-Atifi, Muhammad Fadl Abd al-Nabi, Muhammad Ali al-Qadiri and Muhammad Ahmad al-Talibi are all accused of assisting or sponsoring acts of terrorism, according to U.S. Treasury.

The Houthis have repeatedly launched attacks on ships in the Red Sea since November over Israel’s war on Hamas in the Gaza Strip, though they have frequently targeted vessels with tenuous or no clear links to Israel, imperiling shipping in a key route for global trade.

The sanctions block access to U.S. property and bank accounts and prevent the targeted people and companies from doing business with Americans.

Members of a former rebel group originally from the remote mountains of northwest Yemen, Houthi leaders are generally seen as having few assets within reach of U.S. authorities to be affected by the sanctions. But Middle East analysts say the sanctions may have impact simply by reminding movement leaders that the U.S. knows who they are, and may be tracking them.

Abdel Malek al-Houthi, a Yemeni politician who serves as the leader of the Houthi movement, said Thursday in a speech: “Since the beginning of the offense, with aid raids on our country, and missiles strikes from the sea, the Americans were not able to stop our strikes in the sea and our targeting of ships. But they got themselves, as well as the British, in this problem (conflict).”

State Department official Matthew Miller said in a statement that the U.S. “is continuing to take action to hold the Houthis accountable for their illegal and reckless attacks on vessels in the Red Sea and Gulf of Aden.”

“The Houthis’ terrorist attacks on merchant vessels and their civilian crews in the Red Sea and the Gulf of Aden have disrupted international supply chains and infringed on navigational rights and freedoms,” Miller said.

As recently as Wednesday, two American-flagged ships carrying cargo for the U.S. Defense and State departments came under attack by Houthi rebels, U.S. officials said, with the U.S. Navy intercepting some of the incoming fire. The U.S. and the United Kingdom have launched multiple rounds of airstrikes seeking to stop the attacks.

Treasury Under Secretary Brian E. Nelson said Thursday’s joint action with the U.K. “demonstrates our collective action to leverage all authorities to stop these attacks.”

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Associated Press reporters Ellen Knickmeyer, Jon Gambrell and Jack Jeffrey in London contributed to this report.