KYIV: Russia mounted an intense missile and drone barrage of the Ukrainian capital overnight, killing four people, Ukrainian officials said, as powerful explosions reverberated across the city.

The attack followed a warning from Russian President Vladimir Putin, conveyed via U.S. leader Donald Trump, that the Kremlin would hit back after Ukrainian drones destroyed several strategic bomber aircraft in attacks deep inside Russia.

Kyiv mayor Vitali Klitschko said 20 people were injured, 16 of them in hospital, in addition to the four deaths.

The city's metro transport system was disrupted by a Russian strike that hit and damaged tracks between stations, Kyiv's military administration said. Ukraine's state rail company Ukrzaliznytsia said it was also detouring some trains due to railway damage in the region.

In the Solomianskyi district, a Russian drone slammed into the side of apartment building, leaving a gaping hole and burn marks, a Reuters photographer at the scene said.

Falling concrete blocks from the building crushed cars parked below. Two police investigators were examining what appeared to be the drone's engine.

Earlier in the night, Reuters reporters heard the sound of Russian kamikaze drones buzzing in the sky, accompanied by the sounds of outgoing fire from Ukrainian anti-aircraft fire.

Reuters witnesses reported a series of booming explosions powerful enough to rattle windows far from the impact sites.

Some Kyiv residents sought shelter in metro stations, or in underground car parks.

Ukraine's air force said the country had been targeted with drones and missiles overnight.

Russian forces struck industrial facilities and infrastructure in the western city of Ternopil, leaving parts of it without power, mayor Serhii Nadal said.

The regional administration said the attack injured five people and recommended residents stay inside due to a high concentration of toxic substances in the air after a fire.

Five people were injured in the northwestern city of Lutsk where the attack also damaged private homes, educational institutions and government buildings, according to mayor Ihor Polishchuk.

In one of the most audacious attacks of the war between Ukraine and Russia, Ukrainian spies last weekend destroyed some of Russia's strategic bomber aircraft on the ground using quadrocopter drones hidden in wooden sheds.

The Kremlin was planning an unspecified response to the Ukrainian attack on Russian air bases, Trump said after a telephone conversation with Putin on Wednesday.