Kyiv (Ukraine) (AFP) - Ukrainian President Volodymyr Zelensky on Thursday urged his allies to bring about “regime change” in Russia, hours after a Russian drone and missile attack on Kyiv killed 15 people including a six-year-old boy.

The overnight strikes reduced part of a nine-storey apartment block in Kyiv’s western suburbs to rubble and wounded more than a hundred in the capital, authorities said.

The Russian army meanwhile claimed to have captured Chasiv Yar, a strategically important hillside town in eastern Ukraine where the two sides have been fiercely fighting for months.

Moscow has stepped up its deadly aerial assaults on Ukraine in recent months, resisting US pressure to end its nearly three-and-a-half-year invasion as its forces grind forward on the battlefield.

Speaking virtually to a conference marking 50 years since the signing of the Cold War-era Helsinki Accords, Zelensky said he believed Russia could be “pushed” to stop the war.

“But if the world doesn’t aim to change the regime in Russia, that means even after the war ends, Moscow will still try to destabilise neighbouring countries,” he added.

From late Wednesday to early Thursday, Russia fired over 300 drones and eight cruise missiles at Ukraine, the main target of which was Kyiv, the Ukrainian air force said.

One missile tore through a nine-storey residential building in western Kyiv, tearing off its facade, authorities said.

AFP journalists at the scene saw rescuers scouring through a smouldering mound of broken concrete, the belongings of residents scattered among the debris.

“It’s a shock. I still can’t get my bearings. It’s very frightening,” Valentyna Chestopal, a 28-year-old resident of Kyiv, told AFP.

Among the victims was a six-year-old boy who died on the way to hospital in an ambulance, the head of the city’s military administration, Tymur Tkachenko, posted on Telegram.

Kyiv’s mayor, Vitali Klitschko, said Friday had been declared a day of mourning in the capital for the victims.

The Russian army said it had hit a military airfield, ammunition warehouse and drone production facilities with a combined overnight strike using weaponry and drones.

The attack came just days after US President Donald Trump issued a 10-day ultimatum for Moscow to halt its invasion, now in its fourth year, or face sanctions.

- Key capture in east -

Russia said Thursday that it had captured the town of Chasiv Yar, a strategically important military hub for Ukrainian forces in the eastern Donetsk region.

The town “was liberated by Russian forces”, Russia’s defence ministry said in a statement, though a Ukrainian army spokesperson rejected Russia’s claim as “lies”.

Ukrainian military analyst Oleksandr Kovalenko said Russian forces “have full control over the entire northern and eastern part,” of Chasiv Yar, including districts that were hardest to get.

But he added that the fighting for the western side was ongoing, with the situation “very difficult”.

Taking control of Chasiv Yar would be a major military gain for Russia, which has been making incremental but steady territorial gains for months.

Home to around 12,000 people before the war but now largely destroyed, the town could allow Russian forces to advance on remaining civilian strongholds in the eastern Donetsk region.

These include the garrison city of Kramatorsk and Sloviansk, important logistical bases for the Ukrainian military and home to many civilians who have not fled the fighting.

The Kremlin has made the capture of the Donetsk region a priority since it claimed the industrial region as part of Russia in September 2022.

Russia, which denies targeting civilians, had not yet commented on the strike or Zelensky’s call for regime change.

- Anti-corruption bill overturned -

Thursday’s attacks came just hours before Ukrainian lawmakers overturned a highly criticised law that curbed the powers of two anti-graft bodies.

Zelensky, who signed the new bill into law shortly after the vote, reversed course after the legislation sparked the biggest public unrest in Ukraine since Russia’s invasion began in February 2022.

The original law had put the National Anti-Corruption Bureau of Ukraine (NABU) and Specialised Anti-Corruption Prosecutor’s Office (SAPO) under the direct authority of the prosecutor general, who is appointed by the president.

Critics said the move would allow Zelensky to meddle in high-profile corruption cases, while the European Union said bill could derail anti-corruption reforms that are key for joining the bloc.