Yemen’s Houthi rebel group has been branded as a terrorist organisation by the United States following drone and missile strikes on American military and commercial ships in the Red Sea.

“These attacks fit the textbook definition of terrorism,” national security adviser Jake Sullivan said in a statement released Wednesday. “They have endangered US personnel, civilian mariners, and our partners, jeopardised global trade, and threatened freedom of navigation,” according to NBC News.

The Houthis reaffirmed their support for Hamas and began firing missiles toward Israel and attacking ships in the Red Sea after Israel started bombing Gaza.

In response, the US and its allies launched strikes on locations in Yemen that the Houthis, who are backed by Iran, hold.

Sullivan described the designation as “an important tool to impede terrorist funding to the Houthis, further restrict their access to financial markets, and hold them accountable for their actions.”

“If the Houthis cease their attacks in the Red Sea and Gulf of Aden, the United States will immediately reevaluate this designation.” he added.

According to Sullivan, the designation will go into force in 30 days to give the United States time to lessen its effects on the Yemeni people. “The people of Yemen should not pay the price for the actions of the Houthis,” he stated.

The Houthis are a movement that adheres to Zaydism, a branch of Shiite Islam, and they are a sizable clan that originated in Yemen’s northwest Saada province.

The group seized power in the province of Saada in 2011, following the Arab Spring uprisings that broke out across multiple nations. After three years, its forces overran Sanaa, the country’s capital, and drove President Abed Rabbo Mansour Hadi’s administration into exile.