Russia said Wednesday its forces destroyed four Ukrainian military boats carrying up to 50 soldiers in the Black Sea as authorities reported drone attacks from southern Crimea to near the Estonian border.

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

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

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

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

Early Wednesday, Russian defences repelled a “seaborne drone attack near” near Sevastopol Bay in Crimea, the local Moscow-installed governor Mikhail Razvozhayev was cited as saying by TASS.

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

“Anti-submarine… forces have completed their work,” Razvozhayev said, without giving details.

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 Russian-annexed 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.

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

Drone wave

Ukraine launched another wave of drone attacks across Russia, Russian authorities said on Wednesday.

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

The RIA Novosti agency cited the Ministry of Emergency Situations as saying two Il-76 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 region of Pskov was previously targeted by drones in May.

Authorities in the 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.