Ukraine said it had carried out a sea drone attack on a Russian naval base, as footage showed a damaged Russian warship listing heavily in the Black Sea early Friday.

Social media images and videos showed the ship being towed near the Novorossiysk naval base, despite earlier claims by the Russian defense ministry that the attack had been repelled.

A Ukrainian source told CNN that a sea drone with 450 kilograms of TNT had attacked the ship and claimed there were about 100 Russian servicemen aboard.

"A big navy ship Olenogorsky Gornyak was hit," the source told CNN. "As the result of the attack, the Russian ship has received serious damage and is not able to fulfill its duties."

The vessel was identified by the Ukrainian source and Russian military bloggers as the Olenogorsky Gornyak, an amphibious Russian landing ship.

CNN was provided with video showing an unmanned sea drone approaching a ship that appears to match the identity of the one later seen listing in the port of Novorossiysk.

The 36-second video, shot from the sea drone, shows it approaching a ship at night. The video ends just as the drone reaches its target.

Earlier Russia claimed to have intercepted two Ukrainian sea drones, with the defense ministry saying the boats were "visually detected and destroyed by fire from the standard weapons of Russian ships guarding the outer roadstead of the naval base."

This is a developing story, more to follow...