Kyiv did not disclose how the sophisticated aircraft were struck nearly two years since Moscow's full-scale invasion. The Sea of Azov lies roughly 100 km (60 miles) from areas Kyiv holds. Russia's defence ministry had no immediate comment.
Ukrainian army chief Valeriy Zaluzhnyi, who announced the hits on Telegram messenger, posted a video of an aircraft tracking map suggesting the planes were struck over the Sea of Azov, which lies to the east of the occupied Crimean peninsula.
Reuters was unable to verify his statement independently.
Hours after Zaluzhnyi's statement, a Russian military blog which covers air force matters posted an image of the shrapnel-riddled tail section of an Il-22 standing on tarmac and lauded the crew as "real heroes".
The A-50, which first came into service near the end of the Soviet era, is a large Airborne Early Warning and Control aircraft that can scan an area several hundred kilometres across for enemy aircraft, ships and missiles.
Natalia Humeniuk, spokesperson for Ukraine's southern military command, told a briefing that Russia had used the plane extensively to prepare for and conduct long-range missile strikes on Ukraine.
"We expect such a strike (on the A-50) to be fairly painful and, at least, to delay powerful missile strikes," she said.
Some Russian military bloggers said the downing of the A-50 would be a huge loss for Russia's air force, since there was a limited number of the planes in service.
"It will be another dark day for the Russian Aerospace Forces and Air Defense," wrote Rybar, a blogger with nearly 1.2 million subscribers that supports and provides running commentary on Russia's war in Ukraine.
"There are not many A-50s. And the specialists operating them are generally rare. If an aircraft of this type is hit, the crew will not be able to escape."
The Ukrainian defence ministry valued the A-50 at $330 million.
It was not clear how many A-50s Russia has in service.
London-based think tank IISS said in a 2021 report that Russia had nine A-50 aircraft in operation, including four modernised A-50U planes.
The Russian defence ministry said early last year that the modernised A-50U had been carrying out missions during the war in Ukraine.
The aircraft, which goes by the NATO reporting name of Mainstay, can detect more than 300 targets simultaneously, it said. It can detect and track a missile launch at a distance of 800 km and ground and sea targets at 300 km.
(Reporting by Pavel Polityuk in Kyiv, Yuliia Dysa in Gdansk, Lidia Kelly in Melbourne, Max Hunder in London; writing by Tom Balmforth; Editing by Peter Graff, Hugh Lawson and Nick Macfie)
