Ukrainian protesters opened fire on Friday on police between Kiev's Independence Square and the parliament building, a police statement said.
The violence kicked off again as Polish Prime Minister Donal Tusk urged caution about an agreement reached overnight that is understood to include the introduction an early election and a coalition within ten days.
"Participants in the mass disorder opened fire on police officers and tried to burst through in the direction of the parliament building," the statement said.
It did not say whether police returned fire or tried to restrain the protesters.
Opposition leader Arseny Yatsenyuk, speaking in the parliament building about 1 1/2 km (one mile) from Independence Square, said armed police had entered the premises but the deputy speaker said they had been forced back out of the building.
Polish Prime Minister Donald Tusk today that a draft agreement with the Ukraine's presidency has been reached, but urged caution in predicting the end of the political crisis at the Polish riot-torn neighbour.
"The agreement has not yet been reached. What's been settled is the agreement's draft," Tusk told reporters in the Polish parliament.
"Signing the deal gives hope that it will be the starting point, but I would be cautious in predicting the end of the conflict," he added.
Ukrainian President Viktor Yanukovich said today a deal to resolve his country's political crisis had been reached with pro-European opposition leaders after the worst violence since Soviet times.