Attacks from Yemeni territories controlled by the Houthis struck two Liberian-flagged ships in the Bab al-Mandeb Strait on Friday, a US defense official said, underlining the threat to vessels in shipping lanes being targeted by the Iran-aligned group.

A projectile, believed to be a drone, struck one of the vessels, the German-owned Al Jasrah, causing a fire but no injuries, the official said. Two ballistic missiles were fired in the second attack, one of which struck a vessel, causing a fire which the crew was working to extinguish, the official said.

A US Navy destroyer was on its way to aid the vessel, the official said, without naming the vessel.

There were no immediate claims of responsibility.

Yemen’s Iran-aligned Houthis have been attacking vessels in Red Sea shipping lanes and firing drones and missiles at Israel since the start of the Israel-Hamas war in Gaza, in a campaign they say aims to support the Palestinians.

A spokesperson for Hapag-Lloyd, the company that owns Al Jasrah, said it was attacked while sailing near the Yemeni coast. “Hapag-Lloyd will take additional measures to secure the safety of our crews,” the spokesperson added, declining further comment.

At least two other shipping incidents were reported in the area on Friday.

British maritime security firm Ambrey said a Liberia-flagged container ship, MSC ALANYA, was ordered to alter course toward Yemen by people aboard a small craft assessed to be members of Yemen’s Houthi movement, forcing it take evasive measures.

A spokesperson for MSC said there was no attack on the vessel and had no further comment.

Ambrey said the MSC ALANYA was warned by the Houthis not to proceed northbound, and quoted them addressing the crew: “Captain you are not allowed to proceed to the Red Sea. Alter your course to the south side, now.”

In another incident, Ambrey reported that the Liberia-flagged, Swiss-owned containership MSC PALATIUM III was targeted while sailing northbound some 23 miles southwest of the Mokha.

A spokesperson for MSC declined to comment when contacted about the report.

Ambrey said the vessel, which was on route to Saudi Arabia, had received the same warning as the ALANYA. It did not say who had targeted it.

The Houthis, who rule much of Yemen, have vowed they will continue with their attacks until Israel stops its offensive in the Gaza Strip

Late on Thursday, the Houthis claimed to have carried out a military operation against a Maersk container vessel, directly hitting it with a drone. The Danish shipping company denied the claim and said the vessel was not hit.

The US Special Envoy for Yemen, Tim Lenderking, told Reuters on Thursday that Washington wanted the “broadest possible” maritime coalition to protect ships in the Red Sea and signal to the Houthis that attacks would not be tolerated.

Iran’s Defense Minister Mohammad Reza Ashtiani warned that the proposed multi-national naval force would face “extraordinary problems” and nobody “can make a move in a region where we have predominance.”