Russia is intensifying its offensive in eastern Ukraine.

A Ukrainian nuclear power firm released footage that is said to have been filmed in the city of Enerhodar, which hosts the Zaporizhzhia nuclear plant.

Large explosions can be heard and white columns of smoke are rising.

Residents were holding a protest rally at the time, and four people were injured.

Russia's Defence Ministry says it conducted a missile attack on Saturday on an oil refinery in the southern port city of Odesa.

Ukraine's deputy defense minister says Ukrainian troops have regained control of the Kyiv region.

The minister said Bucha is one of the cities that has been liberated from Russia. The mayor of Bucha says more than 300 residents have been killed.

Ukraine's President Volodymyr Zelenskyy is urging evacuees not to return to their communities until their safety has been confirmed. He says Russian forces have planted landmines all over the place.

An international non-governmental organization, Human Rights Watch, says Russian forces used antipersonnel landmines in violation of a global treaty. More than 160 countries and territories have joined the pact, but Russia has not.

CNN quotes several US officials as saying that Russian President Vladimir Putin is reportedly trying to focus on gaining control of eastern Ukraine in a bid to demonstrate victory.

They were also quoted as saying that the timing for Putin to meet this goal is considered to be May 9th, a Russian holiday to commemorate its victory over Nazi Germany in World War Two.

Russia's chief negotiator said on Sunday that negotiations would continue the following day. But he noted that work on compiling a draft agreement has been largely delayed, suggesting there still is a wide gap between the two sides.