It said 14 members of the crew were rescued and taken to the Spanish port of Cartagena but two others were missing.

Ursa Major left port in St Petersburg 12 days ago, according to Russian news agency Interfax.

The ship’s owner said it was on its way to Vladivostok in Russia’s Far East carrying two cranes for the port weighing 380 tonnes apiece, although the destination could not be confirmed independently.

Ursa Major was in the same area of the Med as another sanctioned Russian ship, Sparta, when it ran into trouble and the two ships had been spotted heading through the English Channel last week, reportedly under escort.

Earlier this month, Ukrainian military intelligence (HUR) reported that the Sparta was heading to Russia’s naval base on the Syrian coast at Tartous to move military equipment out of Syria after the downfall of Bashar al-Assad.

A Kremlin official said on Monday that Russia was in contact with Syria’s new rulers on the future of its two military facilities. at both diplomatic and military level.

Ursa Major’s owner Oboronlogistika has been heavily involved in transporting cargo to Tartous, although Sparta’s reported destination on Tuesday was Port Said in Egypt.

On Monday, the HUR reported that the Sparta had broken down off Portugal, but the problem had been fixed. Ursa Major was also known as Sparta III, so it was not clear which ship it was referring to.

It is not known what caused the explosion on Ursa Major as it passed between Oran in Algeria and the Spanish town of Aguilas. However, unverified video showed the ship listing badly on Monday.

It was built in 2009 and placed under sanction after Russia’s full-scale invasion in Ukraine in 2022 because of the ship owner’s role in delivering cargo to the Russian military.

Oboronlogistika said the cargo ship, which it described as the flagship of its fleet, was carrying 45-tonne hatch covers for icebreakers, as well as the large cranes for the port in Vladivostok.

Rescuers from non-governmental organisation Compass Collective said they were on their way to another emergency when they heard her calls for help.

The unnamed girl, from Sierra Leone, told them she had set off with another 44 people from Sfax in Tunisia. Their boat had sunk and all the other migrants were presumed dead.

Thousands of migrants trying to reach Europe die during the treacherous journey in the Mediterranean every year.

Compass Collective spokeswoman Katja Tempel told the BBC that rescuers on board the Trotamar III vessel had found the young Sierra Leonean migrant wearing a simple life jacket and two tyre inner tubes around her waist at around 03:20 (02:20 GMT) on Wednesday.

The girl told them that the metal boat she had been on had sunk within seconds as strong storms with 3.5m-high (11.5ft) waves hit and that she – and two others – were together in the water for a while but then lost contact.

Rescuers handed her over to Italian authorities on the island of Lampedusa, where she was able to walk as well as talk.

The International Organization for Migration (IOM) says 30,955 migrants have died – or remain missing – crossing the Mediterranean since it started recording figures 10 years ago.

Italy has borne the brunt, receiving more than 63,000 this year alone, according to data released by the UN refugee agency, UNHCR.

The numbers have dropped, however, partly due to the hard-line policies of the right-wing Italian government of Prime Minister Giorgia Meloni.

Many are still missing, according to witnesses, and the coastguard has launched a search operation on Saturday assisted by vessels and aircraft.

An Italian frigate and helicopters were operating at the site, with more ships heading to the area.

In separate incidents on Saturday, a Malta-flagged cargo vessel rescued 47 migrants from a boat sailing about 40 nautical miles (74km) off Gavdos, while a tanker rescued another 88 people some 28 nautical miles (52km) off the island.

According to initial information, coastguard officials believe the boats left together from Libya.

Greece received nearly one million migrants from the Middle East, Africa and Asia in 2015-2016, most of whom took the dangerous route of crossing the sea on inflatable dinghies.

Similar shipwrecks off Crete and Gavdos, which are relatively isolated in the central Mediterranean, have increased over the past year.

According to the Ministry of Migration, Greece has seen a 25-percent increase this year in the number of people entering, fleeing war and poverty, with a 30-percent increase to Rhodes and the southeast Aegean.

Several similar deadly accidents have struck in recent weeks.

In late November, eight people, six of them minors, died north of the island of Samos, on a route frequently used by people smugglers.