Pro-Russian militants on Sunday tried to storm the police headquarters in the Ukrainian Black Sea city of Odessa, where 42 people died in clashes two days ago.

At the police station, activists reportedly broke windows, forced open its gate and entered an interior courtyard. Ukrainian authorities responded by releasing some people detained in last week's deadly clashes. The Interior Ministry said in a statement that 67 people who were detained were released, but it was not immediately clear whether others were still being held.

According to news agency AFP, more than 2,000 pro-Russian militants, some armed with batons, surrounded the complex. In a bid to appease the crowd, police freed some of the pro-Russians arrested during Friday's clashes.

Odessa, a scenic Black Sea port home to more than one million people, remains in shock after running battles on Friday between pro-Russians and pro-Kyiv protesters that culminated in an inferno that left 38 dead.

The majority of those trapped inside the trade union building in central Odessa were thought to be pro-Russian supporters who had barricaded themselves in it.

Tragedy for 'all Ukraine'

Visiting Odessa on Sunday, Ukrainian Prime Minister Arseniy Yatsenyuk described Friday's events as a "tragedy for all Ukraine."

He told a press conference that police were being investigated for their failure to maintain order during Friday's violence, and he claimed that Moscow had had a hand in the events.

"What happened in Odessa was part of plan by the Russian Federation to destroy Ukraine and its statehood," Yatsenyuk said.

"Russia sent people here to create chaos."

At least 42 people died in Friday's unrest - some from gunshot wounds, but most in the fire that tore through a trade union building.

Kyiv presses offensive

Ukraine's Kyiv-based interim government continued on Sunday to deploy helicopters and tank units against pro-Russian separatists in the country's eastern regions.

Intermittent gunfire was still reported in Slavyansk, where OSCE observers were freed on Saturday.

Interior Minister Arsen Avakov was quoted by the German news agency DPA as saying troops had entered government buildings occupied by pro-Russian separatists in Mariupol, another city in the country's southwest.

bk/ipj (Reuters, AP, AFP)