"Today, March 5, from 10 am Moscow time (0700 GMT), the Russian side declares a regime of silence and opens humanitarian corridors for the exit of civilians from Mariupol and Volnovakha," it said.

The ministry clarified that the location of the humanitarian corridors and exit points had been determined in agreement with the Ukrainian authorities, according to Russian news agencies.

Russian forces have been operating in Ukraine since February 24.

The announcement came after Mariupol's mayor Vadim Boychenko said Saturday that the city was under "blockade" and asked for humanitarian corridors. Pro-Russian separatist forces and the Russian military had said the town was surrounded.

Mariupol, a city of about 450,000 people on the Azov Sea, is a strategic port city allowing important maritime access and its capture could see Moscow's troops coming from annexed Crimean peninsula connect with the forces of separatist-controlled Donbas.

Volnovakha is a town of around 20,000 people situated near Ukraine's former frontline with Russian-backed separatists and around 60 kilometres (38 miles) from separatist-controlled Donetsk, a regional centre.