Ukraine's military says its air force has destroyed a Russian Beriev A-50 surveillance plane and an Ilyushin Il-22 airborne command post in the Sea of Azov area in an operation that could delay some future Russian missile strikes.
Ukraine did not disclose how the sophisticated aircraft were struck.
The Sea of Azov lies roughly 100km from areas Ukraine 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 posted an image of the shrapnel-riddled tail section of an Il-22 standing on tarmac and lauded the crew as "real heroes".
Ukraine's air force spokesman reposted the image, saying the plane appeared to have made it to the Russian town of Anapa but that it was beyond repair as it had been on fire.
He added that the A-50 had been Ukraine's priority target.
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.
The planes are key tools in helping orchestrate Russian battlefield movements in Ukraine.
Shooting them down would be a landmark feat for Ukraine in the almost two-year war, as fighting along the front line is largely bogged down in trench and artillery warfare.
Natalia Humeniuk, spokeswoman 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.
"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 aircraft 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 Defence," 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 $US330 million ($A496 million).
Ukrainian military spy chief Kyrylo Budanov told the Financial Times that Russia had eight A-50s left.
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 800km and ground and sea targets at 300km.
with AP
