The fresh wave of attacks comes as Ukraine advocates for a 30-day ceasefire aimed at facilitating peace negotiations.

Russia and Ukraine each exchanged 307 of their service personnel on Saturday on the second day of a prisoner exchange that, when completed, is set to be the largest such swap in the three-year war between the two countries.

Thousands of troops are taking part in military drills in northern Finland, close to the alliance's border with Russia.

Ukraine pioneered the use of small drones on the battlefield. But in Russia’s Kursk region, Moscow’s fiber-optic cables helped turn the tide.

Rescuers work on a site after a Russian strike on residential neighbourhood in Markhalivka village, Kyiv region, Ukraine on May 25. (AP)

Russian drones and missiles again bombarded cities across Ukraine on Saturday night into Sunday morning despite an ongoing prisoner exchange.

Russian armed forces are creating a “security buffer zone” along the border between Russia and Ukraine, President Vladimir Putin said Thursday.

Russian Foreign Minister Sergei Lavrov cast doubt on Friday over the Vatican as a potential location for peace talks between Russia and Ukraine, saying that the Holy See itself would find it uncomfortable to host two mainly Orthodox Christian nations.