Russian ballistic missiles ‌killed 12 people and injured more than 30 in Kyiv early on Thursday, authorities said, damaging buildings and severing power supply to some parts of the Ukrainian capital.

A fire broke out, and the upper floors of a nine-storey residential block were destroyed in the ​city’s Solomianskyi district, where seven people were killed, Mayor Vitali Klitschko said, calling for Friday to be ​observed as a day of mourning.

Two other districts also suffered damage, Klitschko said on the ⁠Telegram messaging app, with non-residential facilities, warehouses, a school and a children’s hospital hit.

Power company DTEK said it restored ​electricity to more than half of the roughly 90,000 homes left without power in the capital following the attack.

Russia ​has stepped up air attacks on Ukraine in recent months, trying to exploit its smaller neighbour’s critical shortage of interceptors to down ballistic missiles.

Read: Russia hits steel plant in new strikes on Ukraine

The Russian defence ministry said Moscow attacked Kyiv and the surrounding region with airstrikes and drones, hitting facilities producing drone components, ​a military depot and a logistics hub, as well as other targets.

Explosions rip through the city

A Reuters witness reported ​hearing more than a dozen explosions. In the region around the Ukrainian capital, another person was killed, an official said on ‌Telegram.

Ukraine’s emergency ⁠service showed video of servicemen battling a blaze in a building and helping people to escape facilities destroyed during the night in Kyiv.

Ukraine has also increased its attacks on Russia, targeting oil facilities and logistics infrastructure to try to undermine Moscow’s ability to wage war.

Diplomatic efforts have failed so far to yield a lasting ceasefire in the war, ​which started with Russia’s full-scale invasion ​of Ukraine in February ⁠2022.

A drone crashed into NATO and European Union member Romania during the Russian attack on Ukraine, the Romanian defence ministry said on Thursday. A drone also crossed Moldova’s airspace, ​the country’s military said.

Read more: War in Ukraine: battle of perspectives

Ukraine had handed proposals to US negotiators, Steve Witkoff and ​Jared Kushner, for ⁠a plan to end the war, President Volodymyr Zelenskiy said this month, and he has also repeatedly asked for interceptor missiles to ward off missile attacks.

Russia did not receive specific proposals for possible new meetings with US negotiators, foreign ministry spokeswoman Maria ⁠Zakharova told ​the Izvestia newspaper, but added that Moscow would be ready to arrange a meeting ​at short notice.

Witkoff and Kushner were last in Moscow last January and have not yet visited Kyiv.