Regional governor Mikhail Vedernikov, who said he was at the scene of the attack, posted a video on Telegram of a massive fire, with the sounds of explosions and sirens in the background.

A drone attack "has been repelled in Pskov airport," Vedernikov wrote, adding authorities were assessing the damage but there were no casualties.

Pskov is located roughly 800 kilometres (nearly 500 miles) from Ukraine's border and the surrounding region borders EU member states Latvia and Estonia.

There was no immediate comment from the defence ministry but four heavy transport planes were reportedly damaged.

All Wednesday flights at the airport were cancelled, Vedernikov wrote, "until the nature of the possible damage to the runway is clarified."

State news agency TASS, citing emergency services, said that four Ilyushin Il-76 heavy transport planes had been damaged.

Citing air traffic services, TASS also reported that airspace above Moscow's Vnukovo airport had been closed.

The region of Pskov was previously targeted by drones in May.

Moscow and other Russian regions have been targeted in recent weeks by a barrage of Ukrainian drone attacks after Kyiv vowed this summer to "return" the conflict to Russia.

- Black Sea ships -

Moscow later said forces had destroyed four Ukrainian boats carrying up to 50 troops in the Black Sea.

An aircraft "destroyed four high-speed military boats" around midnight Moscow time (2100 GMT), the Russian defence ministry wrote on Telegram.

The ministry said the boats had been carrying "landing groups of Ukrainian special operations forces with a total number of up to 50 people."

It did not give details on exactly where in the Black Sea the incident took place.

Both Ukraine and Russia have ramped up activity in the area after a United Nations-brokered deal to ensure safe navigation for grain ships in the Black Sea collapsed last month.

Russia has since pounded Ukraine's port infrastructure on the sea and on the Danube River.

Kyiv has attacked Russian ships in its waters and the Crimean Peninsula, which was annexed by Moscow in 2014.

Last week, Moscow's defence ministry said one of its jets destroyed a Ukrainian "reconnaissance boat" near Russian gas production facilities in the Black Sea.

It later said it also destroyed a US-made speedboat carrying Ukrainian troops east of Snake Island, without providing further detail.