KYIV, July 23 - Russia's latest strike on Odesa on Sunday killed two people and severely damaged a historic Orthodox cathedral, drawing a vow of retaliation from Ukraine's leader.

The attack came as President Vladimir Putin met his Belarusian counterpart for talks in Russia and claimed Kyiv's counteroffensive had "failed,” AFP reported.

Russia has pounded the Ukrainian port city of Odesa since quitting the Black Sea grain deal last week.

Locals watched in disbelief as the Transfiguration Cathedral -- originally built in 1794 under imperial Russian rule -- was hit.

The biggest Orthodox church in Odesa lies within the UNESCO-protected historic city center.

UNESCO condemned the "brazen" attack, which hit several sites in the World Heritage area, marking "an escalation of violence against (the) cultural heritage of Ukraine", according to UNESCO chief Audrey Azoulay.

Clergymen rescued icons from rubble inside the badly damaged shrine, which was demolished under Stalin in 1936 and rebuilt in the 1990s after the collapse of the Soviet Union.

The culture ministry said it had so far identified damage to 29 monuments of important cultural heritage.

The Ukrainian government condemned the cathedral strike as a "war crime", saying it had been "destroyed twice: by Stalin and Putin".

President Volodymyr Zelensky vowed retaliation: "They will definitely feel this," he said.

"We cannot allow people around the world to get used to terrorist attacks," Zelensky added in his evening speech late on Sunday.

"The target of all these missiles is not just cities, villages or people. Their target is humanity and the foundations of our entire European culture."

Images showed smashed mosaics on the cathedral floor as workers cleared the rubble. The outside of the building appeared intact.

"There was a direct hit to the cathedral," said Father Myroslav, the assistant rector, adding that three altars were ruined.

Icons were pulled out from under the rubble and the shrine was "very badly damaged inside", with "only the bell tower intact", he added.

Clergymen said a security guard and a priest getting ready for a morning liturgy were inside during the attack but both survived.

Russia blamed the cathedral damage on Ukrainian air defence. It said it had hit all its intended targets in the Odesa strike, claiming the sites were being used to prepare "terrorist acts" against Russia.

But local people said Russia had hit residential areas.

"We have ordinary residential buildings here, where people live," a woman who owns a beauty salon nearby, Tetiana, told AFP.

"There are no military facilities here. Just simple beauty salons, a marine agency, a groomer. Nothing military here at all."

Russia launched a wave of attacks on the Black Sea port this week, after exiting a deal between Moscow, Kyiv, Istanbul and the UN allowing the safe passage of cargo ships.

Ukraine has vowed to find a way to continue exports from the ports and said Sunday repeated Russian strikes on Odesa this week were an attempt to "prevent and neutralize international efforts to restore the functioning of the "grain corridor." (afp/ez)