Ukraine said on Wednesday it destroyed a Russian S-400 anti-aircraft system on the Crimean peninsula, which was annexed by Russia in 2014. 

"At about 10 am an explosion occurred... destroying a Russian long- and medium-range S-400 Triumph air defence system," the Ukrainian defence ministry said on social media. 

The ministry published a video of a massive explosion with a huge column of smoke billowing into the sky.

It said the explosion took place near the village of Olenivka on the Tarkhankut Peninsula and destroyed "the system, its missiles and personnel."

"This is a painful blow to the occupiers' air defence system," the ministry added.

There were no immediate comments from Moscow, but Russian military bloggers said the attack highlighted flaws in Russia's defence capacities.

The influential Rybar Telegram channel, which has 1.2 million followers, said the strike destroyed a S-300 system. 

"Again, the question arises of why Ukrainian boats come so close to the shores of Crimea. They did this more than once," Rybar said. 

Russia on Tuesday said it destroyed two Ukrainian boats in the Black Sea, but the account said the manoeuvre was "not enough".

"We need a systematic defeat of the entire Ukrainian fleet, and this requires changes in the organisation of the Russian Navy," Rybar said.

Another channel, Voenny Osvedomitel, said the attack "raises fair questions about the quality of air defence coverage in one of the most 'missile-prone' regions of Russia."

Both channels speculated that the attack was carried out with a missile and drones.

Russian-controlled territory has been targeted by daily drone attacks in recent weeks. 

Early morning Wednesday, Moscow was hit by drones for the sixth night in a row.

Later, Vladislav Shapsha, the governor of the Kaluga region south of Moscow said air defence systems in his region had fended off two drones.