Houthi militants in Yemen said on Monday they had attacked the Rubymar cargo ship in the Gulf of Aden and the vessel was now at risk of sinking - raising the stakes in their campaign to disrupt global shipping in solidarity with Palestinians in the Gaza war.

The crew are safe, Houthi military spokesperson Yahya Sarea said in a statement. The Houthis had also shot down a U.S drone in the port city of Hodeidah, he said.

"The ship was seriously hit which caused it to stop completely. As a result of the extensive damage the ship suffered, it is now at risk of sinking in the Gulf of Aden," Sarea said.

The Rubymar sustained damaged after two missiles were fired at the vessel from Yemen although the crew were able to evacuate, the vessel's maritime security company LSS-SAPU told Reuters on Monday.

"We know she was taking in water," LSS-SAPU said when asked about the vessel's condition.

"There is nobody on board now," LSS-SAPU said. "The owners and mangers are considering options for towage."

So far, no ships attacked have been sunk or any crew killed but there are growing safety fears.

Iran-aligned Houthi forces have made repeated drone and missile attacks since mid-November against international commercial shipping in the Red Sea and the Bab al-Mandab Strait - a route that accounts for about 12% of the world's shipping traffic.

The militia has vowed to continue their attacks as long as Israel continues to commit "crimes" against Palestinians.

The Belize-flagged, British-registered and Lebanese-operated general cargo ship came under attack in the Bab al-Mandab Strait off Yemen on Sunday, British maritime security firm Ambrey said.

The UK Maritime Trade Operations agency reported on Sunday that the crew had abandoned a ship off Yemen after an explosion - apparently the same incident.

In a second incident in hours, a Greece-flagged, U.S. owened bulk carrier was attacked on Monday by missiles in two separate attempts, with no injuries to the crew although one window onboard was damaaged, Greek shipping ministry sources told Reuters.

The vessel was sailing from Argentina to Aden with grain with 23 crew members onboard inclduing 5 Greek nationals, the ministry source said.

The attacks have prompted several companies to halt Red Sea voyages and take a longer and more expensive route around Africa. U.S. and British warplanes have carried out retaliatory strikes across Yemen.

Seafarers remain in the firing line, and have already signed agreements to refuse to sail on ships passing through the Red Sea and receive double pay double pay when entering the high-risk zones.

Shipping industry associations on Monday called for the immediate release of the 25 crew members of the Galaxy Leader, which was hijacked by the Houthis on Nov 19, marking three months since their capture.

"The 25 seafarers who make up the crew of the Galaxy Leader are innocent victims of the ongoing aggression against world shipping, and their plight is a major concern as the merchant shipping community continues to come under attack," the associations said in a joint statement.

"It is abhorrent that seafarers were seized by military forces and that they have been kept from their families and loved ones for too long."

The CEO of QatarEnergy, Saad al-Kaabi, said on Monday that disruption to shipping in the Red Sea region would impact its deliveries of liquefied natural gas (LNG) but not its production.

"It's only going to take longer to get it there. But it will not reach a point where we have to stop production because there isn't any ship. We're okay," Kaabi said at a groundbreaking ceremony at the Ras Laffan petrochemical complex.

One of the world's largest exporters of LNG, QatarEnergy said in January it had stopped sailing via the Red Sea for security reasons.

Houthi militants in Yemen, who control the country's most populous regions, have targeted vessels with commercial ties to the United States, Britain and Israel, shipping and insurance sources say.

War risk insurance premiums have been creeping higher and are now around 1% of the value of the vessels with various discounts, which still works out at hundreds of thousands of dollars of additional costs per voyage, insurance sources said.

"As a result of the significantly increased risk in the Red Sea and Gulf of Aden area, additional premiums for war risks have risen dramatically," insurance broker Gallagher Specaility Marine said in a report last week.

"Shipping companies must weigh up the increased costs and journey times against the risk to their vessels, and, most importantly, the safety of the crew onboard."

(Reporting by Ahmed Tolba, Hatem Maher and Yomna Ehab in Cairo and Ahmed Elimam in Dubai,Lisa Barrington in Singapore, Jonathan Saul in London, Andrew Mills in Ras Laffan and Renee Maltezou in Athens; Writing by Michael Georgy and Jonathan Saul editing by Angus MacSwan)