A Russian missile has hit a tanker that has been drifting in the Black Sea for over four months and had been carrying diesel, the Interfax-Ukraine news agency reported on Thursday, citing Ukraine's military which called the ship an "ecological bomb."

The Moldova-flagged tanker Millennial Spirit has now been struck twice since Russia invaded Ukraine on Feb. 24.

It was first hit with a missile fired from a warship days after the invasion. Moldova said at the time that the ship had a Russian crew and two were seriously wounded.

Ukraine's southern military command said when the vessel was struck in February it had more than 500 tonnes of diesel on board and that since then it had been drifting without a crew.

"Probably the remainder of the cargo is burning," the military said in a statement cited by Interfax-Ukraine saying the tanker had been hit for a second time.

It called the vessel a "delayed-action ecological bomb" and blamed the fact it was drifting without a crew on a Russian blockade of Ukrainian ports. It said a Russian Kh-31 air-to-surface missile had struck the ship.

Details of the attack could not immediately be confirmed independently by Reuters.

Ukraine says Russia's invasion has resulted in huge environmental damage and plans to seek compensation in international courts.

Environmental threats from the invasion cited by Ukraine include pollution of water basins.