The Kairos was struck in the south-west area of the Black Sea and the Virat in a central area further east. Both are on a list of ships subject to sanctions, according to London Stock Exchange data.
Sources told BBC Ukrainian that Sea Baby drones were used in the attack – a type of naval drone produced by Ukraine’s security services, known as the SBU.
Turkish authorities said they had been assisting the vessels, and released footage showing two Turkish boats trying to extinguish the fire on the Kairos.
The attacks are seen as a warning by Ukraine, suggesting that ships carrying Russian oil in the Black Sea face the risk of direct attack, not just Western sanctions.
Separately, a major consortium transporting oil from the Caspian region said it had suspended loading in the Russian Black Sea port of Novorossiysk, after an attack by unmanned boats overnight.
The Caspian Pipeline Consortium said the attack had caused significant damage to a mooring point. Russia and Kazakhstan are major stakeholders in the company, which is also part-owned by Western firms like Exxon Mobil, Chevron and Shell.
Meanwhile, Ukrainian President Volodymyr Zelensky said on Saturday that a delegation led by top security official Rustem Umerov was on its way to the US to continue talks on an agreement to end the war.
Umerov is set to lead the Ukrainian delegation after the previous lead negotiator, Zelensky’s influential chief of staff Andriy Yermak, resigned after anti-corruption detectives searched his apartment on Friday.
The Ukrainian delegation is expected to meet American officials in Florida on Sunday. Steve Witkoff, US President Donald Trump’s overseas envoy, will hold talks in Moscow next week.
