At least six people were killed by Russian attacks on the capital and the eastern region of Sumy, Ukraine officials said Monday, after dozens of drones were launched at Kyiv.

"As of now, the number of people killed as a result of a kamikaze drone attack on a residential building has increased to three. Nineteen people have been rescued. (Rescue) work is ongoing," the deputy head of the presidency, Kyrylo Tymoshenko, said on social media.

Kyiv mayor Vitali Klitschko said two of the people killed in the capital were a young married couple.

"A husband and wife who were expecting a child. The woman was six months pregnant," he said on social media.

In the eastern region of Sumy the regional governor meanwhile said three people had been killed and several more were injured.

"At 5:20 (0220 GMT) in the morning, three Russian rockets hit a facility of civil infrastructure. At least three people died. Nine are injured. There are still people under the rubble," Sumy regional governor Dmytro Zhyvytsky said on social media.

Prime Minister Denys Shmygal earlier said Russian strikes had hit energy facilities in Sumy and the central Dnipropetrovsk region, where, according to the presidency, attacks had left some people killed and injured.