Russia launched a strong and ongoing attack on Kiev overnight, with missiles and drones targeting the Ukrainian capital.

By dawn Friday, authorities in Kiev reported four people were killed and 20 injured, and 16 of them were hospitalized.

"Four people have been confirmed to die in the capital. Search and rescue operations are underway at several locations," Mayor Vitali Klitzko said in a telegram.

The city’s military authority said operations of the city’s subway transport system were damaged as Russian strikes attacked and damaged trains between stations.

The air strikes also sparked fires in residential buildings in different parts of the city.

The attack came after Russia vowed to take revenge on Ukraine, following a drone attack on the country's bomber fleet.

Earlier that night, as the attack occurred, Reuters reporters could hear the sound of Russian wind blowing drones buzzing in the sky, accompanied by the outbreak of Ukrainian air defense fires.

Reuters witnesses reported a series of thriving explosive forces were enough to shake windows away from the impact site, and at least a fire broke out in the location hit by the drone.

The Ukrainian Air Force said the city was targeting drones and Kalipur cruise missiles.

Kiev military administration head Tymur Tkachenko said the drone hit the upper floor of a high-rise apartment building and caught fire in the Darnytskyi district on the east side of the city, saying it could reduce emergencies.

An informal telegraph channel said a shopping mall in the area was burning.

Tkachenko said a fire broke out in an apartment building in the western region. He said drone debris was found in three areas.

In one of the most daring attacks in the war between Ukraine and Russia, Ukrainian spies hid Quadrocopter drones in wooden sheds last weekend, destroying some of Russia’s strategic bomber aircraft.

U.S. President Donald Trump said after a telephone conversation with Russian leader Vladimir Putin that the Kremlin is planning an unspecified response to Ukraine's attack on Russian air bases.

Trump said on Thursday it would be better to let Ukraine and Russia "fight for a while" rather than seeking peace immediately.

Trump expressed doubts about the potential success of the peace talks, saying: “Sometimes it’s better to let them fight for a while and then pull them away.”

The U.S. president said he had told Putin that when the two countries called by phone on Wednesday, it was like "two young children fighting wildly in the park."