A Russian cargo ship called Ursa Major sank in the Mediterranean Sea overnight after an explosion ripped through its engine room and two of its crew are still missing, the Russian Foreign Ministry said on Tuesday.

The vessel, built in 2009, was controlled by Oboronlogistika, a company that is part of the Russian Defence Ministry's military construction operations, which had previously said it was en route to the Russian far eastern port of Vladivostok with two giant port cranes lashed to its deck.