Kyiv [Ukraine], December 1 (ANI): Ukrainian underwater drones have struck two tankers belonging to Russia's so-called shadow fleet in the Black Sea, a Ukrainian security official has confirmed -- marking the latest escalation in Kyiv's campaign to disrupt Moscow's oil exports, CNN reported.

Ukraine claimed responsibility after explosions hit the vessels on Friday and Saturday. A security source confirmed that Sea Baby maritime drones were used in a joint operation involving Ukraine's Security Service (SBU) and its navy. Russia has not issued any immediate response.

According to the Ukrainian source, both tankers suffered critical damage and were effectively knocked out of operation. 'This will deal a significant blow to the transportation of Russian oil,' the source said.

Russia uses hundreds of tankers - many sailing under different flags of convenience - to ship its oil to customers in defiance of sanctions, as per CNN.

One of the targeted vessels, the Gambian-flagged tanker Virat, was struck for a second time on Saturday after already sustaining damage the previous day, Turkey's Transport Ministry said.

Turkish maritime authorities reported minor damage above the waterline and confirmed there was no fire on board. The ship was roughly 30 miles (50 km) off the Turkish coast at the time. Tracking data showed it slowing down and turning toward land late Friday, according to CNN.

'There is no request from the personnel to abandon the ship,' the Turkish transport ministry said, but a firefighting tugboat had been sent to the scene.

The Turkish foreign ministry later voiced concern over the attacks, saying they posed 'serious risks to the safety of navigation, life, property, and the environment in the region.'

Virat's destination remained unclear. Shipping data indicated it was waiting for orders somewhere in the Black Sea. The tanker was sanctioned by the United States in January -- under a different name at the time -- and later faced sanctions from both the United Kingdom and the European Union.

A second explosion hit another sanctioned tanker on Friday in a nearby part of the Black Sea. The Gambian-flagged Kairos, which transports Russian crude oil, was severely damaged, and all 25 crew members were evacuated. Neither vessel was inside Turkish territorial waters during the attacks.

Footage from the scene showed Turkish tugs battling a large fire on the Kairos about 30 miles off the Turkish coast. On Saturday, Turkish authorities said the fire on the ship's open deck had been extinguished.

The Kairos, a 275-meter-long tanker weighing nearly 80,000 tons, was sanctioned by the EU earlier this year.

Several unexplained explosions occurred on ships carrying oil to Russia from the Black Sea earlier this year.

Both the Virat and the Kairos had transited the Bosphorus Strait into the Black Sea. Other ships also sanctioned for carrying Russian crude oil were travelling the same route, according to shipping data on Saturday.

There was also an attack by a marine drone early Saturday on a mooring point in Novorossiysk, according to the Caspian Pipeline Consortium.

The pipeline carries oil from Kazakhstan through Russia to customers overseas. Kazakhstan's energy ministry said it had 'activated a plan to redirect export oil volumes to alternative routes' after the strike.

Kazakhstan's foreign affairs ministry issued a statement protesting 'yet another deliberate attack' on the pipeline, saying it harmed relations between the Central Asian nation and Ukraine.

'This incident marks the third act of aggression against an exclusively civilian facility whose operation is safeguarded by norms of international law,' said spokesperson Aibek Smadiyarov.

Novorossiysk has been attacked by Ukrainian drones multiple times. (ANI)