Anger spilled onto the streets in the eastern city of Kharkiv on Saturday as protesters stormed the regional government headquarters, ending the six-day occupation of the building by Ukrainian nationalist activists.

Police stood by as protesters swarmed into the building, beating their opponents and taking prisoners before hoisting Russian and Ukrainian flags at the front door.

Kharkiv is one of several cities across eastern Ukraine where demonstrators with a generally pro-Russian tilt held rallies and raised Russian flags.

The rout occurred during an otherwise peaceful rally in Kharkiv’s Freedom Square, where tens of thousands of people gathered in the morning to protest against the Maidan revolution.

A series of small explosions in the square triggered an angry reaction from the crowd. Hundreds of protesters broke through a police barricade around the regional government building and attacked the occupiers.

The assault on the building was “completely spontaneous,” said Denis Levshinko, a sociology student who participated in the rout of the Maidan occupiers. “We are all fed up with them. We united and we chased them out.”

Levshinko said the protesters clashed with about 500 occupiers, armed with sticks and baseball bats, inside the government building. Many of the activists were taken captive and dragged onto the street, where, forced to their knees, they apologized to the jubilant crowd.

“Beat them, that’s the right thing to do,” shouted one woman. “They should not even be alive.”

“They’re drug addicts,” said another. “You only have to look at their eyes to see they are no better than frozen vegetables.”

Gennady Kernes, the mayor of Kharkiv, called for calm in an address to the demonstration early in the day but left the square when the attack began.

In Donetsk, the hometown of ousted president Viktor Yanukovych, protesters raised a Russian flag on the local administration building. By acclamation, they declared the commander of the Donbass People’s Militia, Pavel Gubarev, to be the new regional governor, according to the Interfax news agency.

But by 3 p.m. the square where the rally took place had emptied.

Russian flags also were reported raised by protesters in Yevpatoria, in Crimea, and in Melitopol and Mariupol, which are on the coast of the Azov Sea to the northeast of Crimea.