Russia kept up its relentless air offensive over Kharkiv early Wednesday, killing three people and injuring at least 60, as Kyiv reiterated its plea for its Western allies to undertake concrete action to pressure Russia into accepting an unconditional ceasefire.

FreshRussianstrikes onUkraine's northeastern city of Kharkiv overnight killed three people and wounded at least 60, among them children, authorities said, asMoscowpushed ahead with its relentless attacks after rejecting an unconditionalceasefire.

"Seventeen strikes by enemy UAVs (drones) were carried out in two districts of the city tonight," Kharkiv Mayor Igor Terekhov said on Telegram adding that "several people were rescued from houses engulfed in flames".

Those are ordinary sites of peaceful life those that should never be targeted, Terekhov wrote on Telegram.

Kharkiv regional Governor Oleg Synegubov said three people had been killed.

The State Emergency Service of Ukraine said eight children were wounded in the attack.

Russia has escalated its bombardments of Ukraine despiteUSPresidentDonald Trumpurging Moscow to end its three-year invasion, withKyivlaunching retaliatory attacks deep inside Russian territory.

Read moreRussia and Ukraine complete second round of ongoing prisoner swap

After a previous overnight barrage of more than 300 drones and seven missiles on Tuesday, Ukrainian PresidentVolodymyr Zelenskyurged Kyiv's Western allies to respond with "concrete action".

"Action from America, which has the power to force Russia into peace. Action fromEurope, which has no alternative but to be strong," Zelensky wrote on social media.

In an interview with the Wall Street Journalon Tuesday, Kremlin aide and key negotiator Vladimir Medinsky said that unless Ukraine agreed to Russia's conditions for an end to the war then Kyiv would lose more territory.

"With Russia, it's impossible to fight a long war," Medinsky told the Journal, citing Russia's 21-year war with Sweden in the 18th Century as evidence that the country prevails in protracted fights.

"We want peace," he was quoted as saying. "But if Ukraine keeps being driven by the national interests of others, then we will be simply forced to respond."

Peace talks in Turkey last weekfailed to yield a breakthroughtowards ending the conflict, with Russia rejecting calls for an unconditional ceasefire and demanding Ukraine give up its territory and bid to join NATO.

But the two sides agreed to swap more than 1,000 prisoners of war and hand over the bodies of dead soldiers, swapping groups of captured soldiers on Monday and Tuesday.

Prisoner exchanges

Kharkhiv, which lies less than 50 kilometres (31 miles) from the Russian border, has been hit by a surge in large-scale nighttime attacks over the past week.

Wednesday's strikes left a five-story building on fire in Slobidskyi district, while several houses were hit in Osnovyansky district, Mayor Terekhov said.

He said "there may be people trapped under the rubble".

The attack came after Russia pummelled the city on Saturday in what Terekhov called "the most powerful attack" on Kharkiv since the start of the war.

Four people were killed and more than 50 wounded as homes and apartment blocks were hit overnight and guided bombs were dropped on the city on Saturday afternoon.

Ukraine is also stepping up its drone attacks on Russia, targeting military production and bases.

On Tuesday, one person was killed and four others wounded in a drone attack that destroyed a convenience store in the Russian region of Belgorod, according to Governor Vyacheslav Gladkov.

Nevertheless, the two sides carried out a second prisoner of war swap on Tuesday.

The deal should see the freeing of all captured soldiers under the age of 25, as well as those who are sick or severely wounded, though neither side has specified the number of soldiers involved.

But Zelensky has said it is "pointless" to hold further talks with the current Russian delegation -- who he previously dismissed as "empty heads" -- since they could not agree to a ceasefire.

As a condition for halting its invasion, Russia has demanded that Ukraine cede the territories Moscow says it has annexed and forswear joiningNATO.

It has also rejected a proposed 30-day unconditional ceasefire sought by Kyiv and theEuropean Union, arguing that this would allow Ukrainian forces to rearm with Western deliveries.

Ukraine is demanding a complete Russian withdrawal from its territory and security guarantees from the West.

(FRANCE 24 with AFP and AP)

Originally published on France24