Russian missile attacks have targeted the Ukrainian cities Kyiv and Kharkiv, killing several people, wounding dozens and damaging residential buildings, officials say.

Kyiv Mayor Vitali Klitschko said 20 people were injured, including a 13-year-old boy. Residential infrastructure was damaged in at least four districts.

In Kharkiv, the country’s second-largest city, four people were killed and at least 40 wounded. An entire section of a multistorey residential building was destroyed, trapping an unknown number of people.

At least one person has been killed and another wounded in a Russian missile strike on Dnipropetrovsk region’s Pavlohrad city, according to the State Emergency Service of Ukraine.

With the front line largely bogged down in eastern Ukraine, Moscow and Kyiv continue to swap air strikes.

Recent Russian attacks have tried to find gaps in Ukraine’s defences, using large numbers of missiles and drones in an apparent effort to saturate air defence systems.

On Sunday, Moscow-installed officials reported that Ukrainian shelling killed 27 people on the outskirts of the Russian-occupied eastern Ukrainian city of Donetsk. Kremlin spokesman Dmitry Peskov labelled the attack a “monstrous terrorist act”.

The Ukrainian military, however, denied it had anything to do with the attack.

It has not been possible to verify either side’s claims.