A senior American official says Russia is planning to hold "sham referenda" and recognize the southern city of Kherson as an independent republic.
The US says Russia is planning to annex a large part of Eastern Ukraine this month, hold "sham elections" and recognise Kherson as an independent republic.
Meanwhile a strike on the city of Odesa on Monday evening killed a teenage boy, officials say.
The first evacuees from a massive steel plant in Mariupol under an operation which began at the weekend had still to reach safety in Zaporizhzhia by Monday night. An estimated 100,000 civilians remain in the port city which has faced constant shelling since early on in the war.
Follow Monday's events as they unfolded on our blog below.