DONETSK, Ukraine (REUTERS) - Pro-Russia activists occupying regional offices in Donetsk, in eastern Ukraine, on Monday proclaimed the creation of a separatist Donetsk republic, a Reuters witness said.

One of the leaders of about 100 activists who moved into the building on Sunday night called for a referendum to be held no later than May 11 on the establishment of the "Donetsk people's republic".

Reading from a text, an unidentified, bearded man said protesters would call on Russia to send in a "peacekeeping contingent" in the event of aggressive action by what he described as the "illegitimate" authorities in Kiev.