For a second day in a row, the U.S. Navy downed four unmanned aerial drones Thursday over the Red Sea, according to U.S. Central Command.

The drones, launched by Houthi militants from areas they control in Yemen, were aimed at a “coalition vessel and a U.S. warship,” between 6 p.m. and 10:56 p.m. local time, according to a news release Thursday from Central Command in Tampa, Fla.

The Navy considered “these weapons… an imminent threat to merchant vessels and U.S. Navy ships in the region,” according to the release. No injuries or damage were reported by U.S. or coalition ships.

The release did not identify any of the vessels involved in the attack.

U.S. and U.K. forces in the Red Sea have struck the Iranian-back Houthis at military targets in areas the group controls in Yemen and at missiles and drones launched at shipping in the Red Sea, a vital commercial waterway

Although more than 20 countries agreed in December to participate in a efforts to safeguard the Red Sea, a vital commercial waterway, not all have sent naval vessels to patrol the area.

On Wednesday, the Navy also downed four Houthi drones that targeted a Navy vessel that Central Command did not identify. Efforts by Stars and Stripes to reach the command by phone and email for further information on Wednesday and Thursday in Florida were unsuccessful.

U.S. Navy vessels have been targeted repeatedly by the Houthis, either by drones or by close-range ballistic missiles. The destroyer USS Laboon, part of the group escorting the aircraft carrier USS Dwight D. Eisenhower, was unsuccessfully targeted March 12 by a missile; in January the destroyers USS Gravely in the Red Sea and the USS Carney in the Gulf of Aden were also targeted but downed both missiles.

The Houthis have claimed the missile and drone attacks on Red Sea shipping are acts of solidarity with Palestinians under attack by Israeli forces in Gaza. Some global shipping firms, including Danish container giant Maersk, have diverted their ships from the Red Sea and along a longer route around the Cape of Good Hope, South Africa, instead.

“Regretfully, both our internal analysis, as well as insight we received from external sources, still indicates that the risk level in the region remains elevated,” the company said in a statement posted March 22 on its website.

It cited the attack March 6 on the True Confidence that killed three crew members, and the attack Feb. 19 on the Rubymar, a cargo ship that later sank with 21,000 metric tons of ammonium phosphate sulfate fertilizer aboard and now poses a navigation and environmental hazard.