Arab coalition forces have launched operations against militia boats of Yemen’s Houthi group that struck a civilian logistics ship on a humanitarian voyage in a strategic Red Sea shipping lane, the Saudi-led alliance said.

The vessel, an Australian-built high speed logistics catamaran under lease to the United Arab Emirates military, was attacked by Houthi fighters near the Bab al-Mandab strait off Yemen’s southern coast on Saturday. The coalition rescued its civilian passengers. No crew were hurt.

In a statement late on Saturday, the coalition said the vessel belonged to the UAE Marine Dredging Company “on its usual route to and from Aden to transfer relief and medical aid and evacuate wounded civilians to complete their treatment outside Yemen.”

“Coalition air and naval forces were targeting Houthi militia boats involved in the attack,” it said.

The coalition said the incident showed that Houthi tactics involved what it called “terrorist attacks” against civilian international navigation in the waterway.

Hundreds of Emirati soldiers in an Arab alliance have been fighting Yemen’s Iran-allied Houthis, who control the capital, and training Yemeni troops in Aden to help rebuild a state loyal to exiled president Abd-Rabbu Mansour Hadi.

The Houthis, however, said on Saturday their forces had destroyed a UAE military vessel that was advancing towards the Red Sea port of Al-Mokha.

“Armed forces destroyed with a missile a military vessel belonging to the forces of the UAE,” a military official was quoted as saying by the Saba Yemeni news agency, run by the dominant Houthi movement since it seized Sanaa last year.

In 2013, more than 3.4 million barrels of oil per day passed through the 20 km (12 mile) wide Bab al-Mandab strait, according to the US Energy Information Administration.

A senior Emirati commander was among dozens killed in a Tochka rocket strike in 2015 on an army camp near Bab al-Mandab, one of the bloodiest setbacks for Gulf forces in months of fighting.