DONETSK, Ukraine — Men in the uniforms of Ukraine's now-defunct riot police are occupying police headquarters in Donetsk, the eastern city that is one of the flashpoints of a wave of pro-Russia protests.

The action came hours after armed men on Saturday seized the police headquarters in Slovyansk, a city about 55 miles from Donetsk. That city's mayor said the men were demanding a referendum on autonomy and possible annexation by Russia.

Witnesses said the men who entered the police building in Donetsk were wearing the uninforms of Berkut, the feared riot police squad that was disbanded in February after President Viktor Yanukovych was ousted and fled to Russia.