Moscow said Tuesday it had destroyed a Ukrainian military "reconnaissance boat" near Russian gas infrastructure in the Black Sea, in the latest clash in the waterway since Moscow's withdrawal from a major grain export deal.

Attacks by both sides have escalated in the Black Sea since Russia in July pulled out of the United Nations-brokered deal that had allowed the safe export of Ukrainian grain through the shipping hub.

Russia has repeatedly bombed Ukrainian port infrastructure in sea and on the Danube, while Ukraine has attacked Russian ships in its waters and the Crimean Peninsula, which was annexed by Moscow in 2014.

A Sukhoi Su-30sm jet from Russia's Black Sea Fleet destroyed a "reconnaissance boat" belonging to Ukraine's armed forces "in the area of Russian gas production facilities in the Black Sea", Moscow's defence ministry said on Telegram.

It did not give details on what kind of boat had been destroyed, or where exactly the incident had taken place.

Late Monday the ministry said its forces downed two Ukrainian drones over the Black Sea, 40 kilometres (25 miles) northwest of the Crimean peninsula.

Earlier this month a Russian tanker was damaged in a Ukrainian drone attack in the Kerch Strait, briefly halting traffic on a strategic bridge linking Crimea to Russia.

- Moscow targeted -

The Moscow region was targeted by Ukrainian drone strikes for a fifth consecutive night, Russian authorities said early Tuesday, although no casualties were reported.

Aerial defence had downed one attack drone each in the Krasnogorsk and Chastsy areas of the region, mayor Sergei Sobyanin wrote on Telegram.

AFP images from Krasnogorsk showed a high-rise residential building with several windows blown out, debris and a damaged car.

Video published by the RIA Novosti news agency showed what its correspondent said were fragments of a drone.

Russia's defence ministry said there had been no casualties in the attack.

Air traffic at Moscow's Vnukovo, Sheremetyevo and Domodedovo airports had been briefly halted, the TASS news agency earlier quoted an aviation service source as saying.

Sheremetyevo and Domodedovo later resumed receiving flights, TASS said.

Two other Ukrainian drones were downed over the Bryansk region near the Ukrainian border early Tuesday, Moscow's defence ministry said on Telegram, adding there were no casualties.

The strikes are the latest in a recent wave of air attacks deep inside Russian territory, including two drones which were shot down near the Kremlin in May.

The aerial threat is also being addressed in the classroom.

Russian teenagers will learn how to operate and counter military drones in the upcoming school year, according to a curriculum published Monday by the education ministry.

Moscow announced last November it was re-introducing Soviet-style military training for children from 2023, as it presses ahead with its nearly 18-month offensive in Ukraine.

- F-16s -

Ukrainian president Volodymyr Zelensky arrived in Greece on Monday at the end of a European tour with stops in Sweden, the Netherlands and Denmark.

Greek Prime Minister Kyriakos Mitsotakis said Athens would help train Ukrainian pilots on American F-16s, days after Kyiv welcomed the decision by the Netherlands and Denmark to provide the fighter jets to Ukraine.

Zelensky had sought the advanced jets for months to strengthen Ukraine's Soviet-era air force as it pursues a grinding counteroffensive against Russian forces in the east.

Training by an 11-nation coalition is to begin this month, and officials hope pilots will be ready by early 2024.

The long-sought F-16 deal has drawn a warning from Russia, with Foreign Minister Sergei Lavrov saying Moscow would consider the jets a "nuclear" threat because of their capacity to carry atomic weapons.