The 58-year-old Saratov joined the Soviet navy in 1964. It can carry up to 20 tanks, or 45 armoured personnel carriers or 50 trucks, as well as up to 400 marines.
The ship is 113m (371ft) long and can carry a load of up to 1,500 tonnes.
Berdyansk lies on the Sea of Azov, between the port city of Mariupol and Crimea. Capturing Mariupol, now in ruins after months of bombardment, was a key strategic goal for the Russian military.
The Ukrainian military took more pride in having knocked out the Black Sea Fleet flagship – the missile cruiser Moskva – in April. Two Neptune missiles were credited with having sunk it, though Russia disputed that, saying the ship sank after a big fire on board.
A Russian landing ship has been destroyed and two other vessels have been damaged in the occupied Ukrainian port city of Berdyansk, said Ukrainian officials.
The Ukrainian military posted footage early on Thursday and said the Orsk had been hit by its forces.
Details of what caused the explosion and fire on board the ship were unclear.
Berdyansk, which is west of the besieged port of Mariupol, was seized four days after Russia invaded Ukraine.
Russia said it had used the port as a base to ferry in equipment for its troops.
Russian army TV hailed the arrival of the Orsk in Berdyansk last week as an “epic event” as it was the first Russian warship to dock there.
Drone footage filmed by Russian state TV reporter, Murad Gazdiev, showed an armoured personnel carrier being offloaded from the Orsk in the port. The armoured vehicles were to be used to reinforce Russian troops, the TV report added.
Video posted by the navy and on social media showed explosions and a big ship on fire at the port at 07:00 (05:00GMT) on Thursday.
While the Orsk was said to have been destroyed, fire reportedly spread to other vessels as well as an ammunition depot and a fuel terminal in the port. Footage from the scene appeared to show two ships sailing at speed from the port. -BBC
