Video of fire and thick smoke coming from the port area was released by Ukraine authorities
Ukraine claims it has destroyed a Russian navy ship capable of carrying 20 tanks, 45 armoured vehicles and 400 troops in the occupied port city of Berdyansk.
Ukrainian deputy defence minister Hanna Malyar told Ukrainian TV the military had sunk the Russian ship Orska in the Sea of Asov, claiming it was a "huge target".
Photos and video online show fire and thick smoke coming from the port area.
The UK's Ministry of Defence appeared to confirm the incident on Thursday night, claiming Ukrainian forces launched strikes against "high-value targets" in Russian-occupied parts - including a landing ship.
But details around the fire are contested and ITV News has not been able to independently verify Ukraine's claim. Russia has not commented on Ukraine's claim and there are suggestions debris from a shot down helicopter could have been the cause of the fire.
Berdyansk has been in Russian control since February 27, just days after the invasion.
In a televised address on February 24, Russian president Vladimir Putin announced the start of what he calls a “special military operation”.
As he spoke, the Russian military unleashed a series of air raids and missile strikes on Ukraine’s military facilities and key infrastructure.
Russian troops rolled into Ukraine from Crimea in the south, all along the eastern border and from Moscow’s ally Belarus, which borders Ukraine in the north.
The Orsk was the first warship to dock in the port city of Berdyansk, which itself was an early prize for the Russians who have made few gains since.