Heraldo de Madrid - Ukraine says Russian strikes hit Kharkiv, killing two

"Seventeen strikes by enemy UAVs (drones) were carried out in two districts of the city tonight," Kharkiv Mayor Igor Terekhov said on Telegram, later adding that 37 people were wounded and "several people were rescued from houses engulfed in flames".

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

Russia has escalated its bombardments of Ukraine despite US President Donald Trump urging Moscow to end its three-year invasion, with Kyiv launching retaliatory attacks deep inside Russian territory.

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

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

Peace talks in Turkey last week failed to yield a breakthrough towards 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 joining NATO.

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

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

C.Diez--HdM