Photo: ShipSpotting.com
By David Gritten & Joshua Cheetham for BBC News
The crew of a Belize-flagged, British-registered cargo vessel have abandoned ship off Yemen after it was hit by missiles fired by the Houthi movement.
The Rubymar was in the Gulf of Aden and nearing the Bab al-Mandab Strait when it was struck, security firms said.
A Houthi military spokesman claimed that the ship suffered "catastrophic damage" and was at risk of sinking.
The UK condemned the "reckless attack" on the Rubymar and said allied naval vessels were "already on the scene".
It is one of the most damaging attacks yet carried out by the Iran-backed Houthis, and is the latest evidence that Western efforts to deter them are yet to succeed.
The Houthis have launched dozens of missiles and drones at merchant vessels and Western warships in the Red Sea and Gulf of Aden since mid-November, in what they say is a show of support for the Palestinians in the war between Israel and Hamas in the Gaza Strip.
The attacks have prompted many shipping companies to stop using the critical waterway, which accounts for about 12 percent of global seaborne trade.
US and British forces began carrying out air strikes on military targets across Houthi-controlled western Yemen in response last month.
On Sunday night, the UK Maritime Trade Operations (UKMTO) agency said it had received a report of an incident from an unnamed ship about 35 nautical miles (65km) south of the Yemeni Red Sea port of Mocha.
The master had reported "an explosion in close proximity to the vessel resulting in damage" at about 23:00 local time (20:00 GMT), it added.
Early on Monday, the agency cited military authorities as reporting that the crew abandoned the vessel following an attack.
"Vessel at anchor and all crew are safe," it said. "Military authorities remain on scene to provide assistance."
British maritime security firm Ambrey separately reported that a Belize-flagged cargo ship had come under attack in the Bab al-Mandab Strait on Sunday as it sailed northwards.
Rubymar's security firm, LSS Sapu, and data provider Lloyd's List Intelligence later confirmed that it had sustained damage after being hit by two missiles.
"We know she was taking in water," a spokesperson for LSS-SAPU told Reuters news agency.
"There is nobody on board now," it added. "The owners and managers are considering options for towage."
According to data from MarineTraffic, which last received a tracking signal on Sunday, the Rubymar had been travelling from Saudi Arabia to Bulgaria.
Houthi military spokesman Yahya Sarea announced in a statement on Monday morning that its naval forces had fired a number of missiles at "a British ship" in the Gulf of Aden, which he identified as the Rubymar.
"The ship suffered catastrophic damage and came to a complete halt," he said, without providing any evidence.
"As a result of the extensive damage the ship suffered, it is now at risk of potential sinking in the Gulf of Aden. During the operation, we made sure that the ship's crew exited safely."
The Djibouti Port Authority said it had co-ordinated the safe repatriation of the Rubymar's 24 crew members - 11 Syrians, six Egyptians, four Filipinos and three Indians - after they were initially assisted by a passing vessel.
Warning over fertiliser
It also warned that the Rubymar had on board almost 22 tonnes of fertiliser - classified as a very dangerous material because it is highly explosive - and was now at an unknown location in the Bab al-Mandab Strait, which is only 32km wide.
The 172m-long Rubymar is flagged in Belize, its operators are from Lebanon and its registered owner is Golden Adventure Shipping, with an address in the British port of Southampton.
The UK government said current reports suggested there were no casualties resulting from the attack.
"Nearby coalition vessels are already on the scene and HMS Richmond continues to patrol in the Red Sea to help protect commercial shipping," a spokesperson added.
"We have been clear that any attacks on commercial shipping are completely unacceptable and that the UK and our allies reserve the right to respond appropriately."
Ambrey also said it was aware that two projectiles had exploded close to a Greece-flagged, US-owned cargo ship about 100 nautical miles east of the southern Yemeni port of Aden on Monday.
The UKMTO said a ship's master had reported two explosions, and that there was "evidence of shrapnel and damage to paintwork".
"The vessel and crew are reported to be safe and proceeding to the next port of call," it added.
Greek shipping ministry sources told Reuters that the vessel was the Sea Champion, whose owner is New York-based MKM Chartering, and that it had been transporting grain from Argentina to Aden when it was attacked.
Later on Monday Sarea claimed the Houthis had targeted two American ships in the Gulf of Aden - the Sea Champion and the Navis Fortuna.
Possible US missions
Sarea also said Houthi air defences in the Red Sea province of Hudaydah had shot down a US MQ-9 Reaper unmanned aerial vehicle (UAV) "while it was carrying out hostile missions against our country on behalf of [Israel]".
There was no immediate comment from the US military.
US Central Command said its forces had carried out five strikes against three mobile anti-ship cruise missiles, one unmanned underwater vessel (UUV) and one unmanned surface vessel (USV) in Houthi-controlled areas of Yemen on Saturday after determining that they presented an imminent threat to US Navy ships and merchant vessels in the region.
It was the first time that US forces had identified a UUV, or submarine drone, being employed by the Houthis since the attacks began.
BBC security correspondent Frank Gardner says the discovery that the Houthis are deploying both USVs and UUVs is a worrying development. The concept of a "swarm attack" - launching a number of relatively cheap missiles and drones simultaneously at an enemy in the hopes of confusing and overwhelming their defences - is straight out of the playbook of the navy of Iran's Revolutionary Guards.
As Houthi attacks on shipping in the lower Red Sea and adjacent Gulf of Aden show no sign of stopping, the prospect of such an attack being directed at a US or British warship is an ever-present threat for those crews now serving there, the BBC's correspondent adds.
In another development, EU foreign ministers meeting in Brussels approved a mission to help protect international shipping in the Red Sea. It aims to have the operation which will involve four ships from France, Germany, Italy and Belgium up and running in a few weeks.
This story was first published by the BBC.