KYIV, Aug 5 (AFP) - A Ukrainian sea drone full of explosives struck a Russian fuel tanker overnight near a bridge linking Russia to annexed Crimea, the second such attack in 24 hours, both sides said on Saturday.

No one was hurt, but the Crimean Bridge and ferry transport were suspended for several hours, according to Russian-installed officials in Crimea, which Moscow seized from Ukraine in 2014.

A Ukrainian intelligence source told Reuters that the drone with 450 kg of explosives hit the SIG vessel as it transported fuel for the Russian military in Ukrainian territorial waters.

"The tanker was well loaded with fuel, so the 'fireworks' were seen from afar," the source said, of the joint operation by Ukraine's navy and security service.

Kyiv says destroying Russia's military infrastructure inside Russia or on Russian-controlled territory in Ukraine is crucial to its counteroffensive after the February 2022 invasion.

Another sea drone attack on Russia's navy base at Novorossiyk damaged a warship on Friday, the first time the Ukrainian navy had projected its power so far from its shores.

And a Ukrainian government agency warned on Saturday that six Russian Black Sea ports - Anapa, Novorossiysk, Gelendzhik, Tuapse, Sochi, and Taman - were in "war risk area".

Moscow has bombed Ukrainian ports since its withdrawal last month from a U.N.-brokered deal to let Ukraine export grain.