The separatist leaders of the Russian-controlled areas of Luhansk and Donetsk in Ukraine have said they are planning to hold votes for the territories to become part of Russia.

The announcements of referendums starting on Friday came after a close ally of Russian President Vladimir Putin said they were needed.

Former president Dmitry Medvedev said that folding Luhansk and Donetsk, in eastern Ukraine, into Russia itself would make their redrawn frontiers “irreversible” and enable Moscow to use “any means” to defend them.

Such votes would almost certainly go Moscow’s way but would not be recognised by western governments.

The votes could set the stage for Moscow to escalate the conflict as Ukrainian forces battle with growing success to take back captured territory.