May 4, 2014 -- Hundreds of pro-Russian demonstrators descended on the police headquarters in Odessa, Ukraine, and stormed the building today, two days after more than 40 people were killed in the city.

As demonstrators swept through the building, groups outside started chanting "Odessa is a Russian city, Odessa is a Russian city."

Sixty-seven people detained, including some well-known pro-Russian figures, were released, according to The Associated Press. The police on site did not fight demonstrators and instead opened cell doors to let people out.

The attack is another event in the escalating violence during political riots in Ukraine. The attack on the police station raised further questions about the government's ability to control security in the south after already dealing with insurgencies in the eastern part of the country.

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Odessa is next to Crimea, which has already been annexed by Russia. The violence has raised concerns that Russian influence extends all the way from the Russian border, down through Crimea and to the Moldova border.

The attack on the police headquarters comes on the same day that Ukrainian prime minister Arseniy Yatsenyuk visited Odessa and asked for calm. On Friday more than 40 were killed from both gunshots and a fire that tore through a trade union building in the city.

"This is not a tragedy only for Odessa," Yatsenyuk said, according to the Associated Press. "This is a tragedy for all Ukraine."

Yatsenyuk called for prosecutors to find "all instigators, all organizers and all those that under Russian leadership began a deadly attack on Ukraine and Odessa."

On Saturday a standoff ended after pro-Russian demonstrators set buses on fire to stop attacks. According to local reports, 10 people were killed.

Odessa's police chief had called for calm on Saturday, but mere hours after issuing the statement he was fired by the Interior Minister.

In more than a dozen cities across eastern Ukraine, official government buildings have been taken over by pro-Russian forces, leading to worries that violence could escalate until a civil war erupts in the country.

The Associated Press contributed to this report.