Ukraine has regained control of "the whole Kyiv region" after invading Russian forces retreated from some key towns near the Ukrainian capital, deputy defence minister Ganna Maliar said on Saturday.

"Irpin, Bucha, Gostomel and the whole Kyiv region were liberated from the invader," Maliar said on Facebook, referring to towns that have been heavily destroyed by fighting.

All three towns lie northwest of Kyiv and have suffered heavy destruction since Russia invaded Ukraine on February 24.

Irpin and Bucha, commuters towns outside Kyiv, were retaken by the Ukrainian army this week.

Both have seen large civilian deaths.

News agency AFP saw at least 20 bodies on a single street in Bucha on Saturday, including one with his hands tied.

The town's mayor said 280 people had been buried in a mass grave in Bucha and that the town is littered with corpses.

Authorities have said that at least 200 people have been killed in Irpin since Russia invaded Ukraine in late February.

Sappers were working to demine the town Saturday, with emergency services saying 643 explosives had been deactivated since Irpin was retaken by Ukrainian forces.

Gostomel, near Kyiv, was the setting of heavy fighting to take control of an airfield.

Ukraine has said Russia is withdrawing from northern areas and appears to be focusing on the east and south of Ukraine.