Ukraine launched an extensive assault on a Russian ship repair base in Crimea early Wednesday morning, Russian and Ukrainian officials said, in what appears to be Ukraine's most ambitious strike on the port since the war began.

Russia's Defense Ministry said Ukrainian armed forces attacked the Sergo Ordzhonikidze shipyard in Sevastopol, which Russia uses as a repair base for its Black Sea Fleet, with 10 cruise missiles and three unmanned boats.

The ministry said its air defense forces shot down seven of the missiles and that the patrol ship Vasily Bykov destroyed all of the boats.

But Russian officials confirmed that the attack had damaged two Russian warships and left 24 people injured.

Mikhail Razvozhaev, Russian-appointed governor of Sevastopol, the largest city in the Ukrainian peninsula of Crimea that was illegally annexed by Moscow's forces in 2014, confirmed the substantial attack. Videos and images purportedly from the area, some posted by Razvozhaev, show a large plume of smoke and a fire raging.

Razvozhaev later said he was at the site "on the southern grounds of Sevmorzavod... As a result of the attack, according to preliminary information, 24 people were injured, with 4 in moderate condition."

One unofficial Russian military blogger also said two ships were damaged: a diesel-electric submarine "Rostov-on-Don" and the large landing ship "Minsk," which caught fire. Both vessels were undergoing repairs in dry dock. CNN could not independently verify the account.

Another unofficial account claimed that Ukraine had used British-made Storm Shadow missiles.

The commander of Ukraine's air force, Lieutenant General Mykola Oleshchuk, said Wednesday: "While the occupiers are still recovering from the night-time bombardment in Sevastopol, I would like to thank the pilots of the Ukrainian Air Force for their excellent combat work! To be continued..."