Kyiv was targeted early Wednesday by the "most powerful" barrage of missiles and drones since the spring, authorities said, with two people reported dead, as Russia claimed it destroyed four Ukrainian boats in the Black Sea carrying up to 50 soldiers.

More than 20 missiles and drones were "destroyed by air defence forces" overnight, the Kyiv City Military Administration wrote on Telegram, describing the aerial assault as "the most powerful" to hit the city since the spring.

An AFP reporter heard at least three loud explosions in the centre of Kyiv around 5:00 am (0200 GMT).

Two people had died as a result of falling debris, Sergiy Popko, head of the Kyiv City Military Administration, wrote on Telegram.

Another person was injured and was being given medical assistance, he said.

Russian forces had launched groups of Iranian-made Shahed attack drones at the capital from different directions, and launched missiles from aircraft, the Kyiv city military administration said.

Earlier, Moscow's defence ministry said a Russian aircraft "destroyed four high-speed military boats" in the Black Sea around midnight Moscow time (2100 GMT Tuesday).

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

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

Early Wednesday, Russian defences also repelled a "seaborne drone attack near" near Sevastopol Bay in Crimea, the local Moscow-installed governor Mikhail Razvozhayev was cited as saying by the state-run TASS news agency.

Sevastopol is the base of Russia's Black Sea fleet.

Both Ukraine and Russia have ramped up activity around the strategic waterway after a United Nations-brokered deal to ensure safe navigation for grain ships collapsed last month.

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

Last week, Ukraine said its forces had flown the country's flag in Crimea during a "special operation" to mark its second wartime Independence Day.

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

- Drone wave -

Ukraine launched another wave of overnight drones strikes on Russia, targeting several regions from an airport near the Estonian border to the Crimea peninsula on the Black Sea, Russian authorities said.

Air defences "repelled" a drone attack on an airport at Pskov, roughly 800 kilometres (nearly 500 miles) from Ukraine's border and close to the borders of EU member states Latvia and Estonia, the local governor said.

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.

Authorities were assessing the damage but there were no casualties, he said.

There was no immediate comment from the defence ministry.

The RIA Novosti agency cited the Ministry of Emergency Situations as saying two Ilyushin Il-76 heavy transport planes had caught fire.

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

Citing air traffic services, TASS also reported that Moscow's Domodedovo and Vnukovo airports had been "temporarily closed" to traffic.

The Pskov region was previously targeted by drones in May.

Authorities in Bryansk region near the Ukraine border, southern Oryol region and Kaluga and Ryazan regions, southwest and southeast of Moscow, all reported drones had been destroyed or downed.

Air defences also destroyed a drone "heading for Moscow," the city's mayor wrote on Telegram, adding there were no casualties or damage caused, according to initial reports.

Moscow and other Russian regions have been targeted by almost daily drone strikes since Kyiv vowed this summer to "return" the conflict to Russia.