DONETSK, Ukraine - About 50 pro-Russian protesters chanting "Donetsk is a Russian city!" broke through police lines on Sunday and stormed inside the main administration building of the eastern Ukrainian city.
The activists moved away from a crowd of about 2,000 rallying on the main city square and threw firecrackers at police surrounding the government seat before raising the Russian flag above the 11-storey building.
An AFP reporter at the scene said security officers pulled a water cannon up to the building but did not use force against the activists.
The action began earlier in the day with calls for Donetsk - a heavily Russified industrial city of one million people that has witnessed weeks of similar Sunday rallies - to stage an independence referendum like the one that led to Crimea's annexation by Russia last month. Some in the crowd chanted "Give us a referendum" and "Nato go home".
The southern and eastern regions of the culturally splintered nation of 46 million have been hit by waves of at times deadly protests that followed the February 22 fall in Kiev of pro-Russian president Viktor Yanukovych and the rise of a team that is seeking closer ties to the West.
The unrest and threat of bloodshed has sparked concern in both Kiev and Western countries that Russian President Vladimir Putin may order his troops into the eastern regions following his promise to "protect" his compatriots there.
Washington believes that Russia has massed about 40,000 soldiers near the eastern border of Ukraine.
Moscow has denied plans to move its troops beyond Crimea but has thus far pulled only a few hundred troops back from the border region.