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Efrem Lukatsky, Associated Press
Ukrainian protesters clash with police after a vote to give greater powers to the east, outside the Parliament, Kiev, Ukraine, Monday, Aug. 31, 2015. The Ukrainian parliament has given preliminary approval to a controversial constitutional amendment that would provide greater powers to separatist regions in the east. Hundreds of people gathered in front of the parliament to protest against the amendment.

KIEV, Ukraine — Clashes broke out between police and nationalist protesters outside the Ukrainian parliament on Monday after a controversial vote to give greater powers to separatist regions in the east. About 100 law enforcement officers were injured, 10 of them seriously, the interior ministry said.

At least some of the officers were injured in the explosion of an object thrown from the crowd of protesters. It was not immediately clear what was thrown, but photographs and video showed it emitting a trail of smoke.

No injuries were immediately reported among the approximately 100 active protesters, most of whom were members of Svoboda, a nationalist party that holds only a handful of seats in parliament.

The decentralization of power was a condition of a truce signed in February aimed at ending the fighting between Ukrainian government troops and Russia-backed separatists that has left more than 6,800 dead. But some Ukrainians oppose changing the constitution, saying that it would threaten the country's sovereignty and independence.

A total of 265 deputies in the 450-seat parliament gave preliminary approval Monday to the changes proposed by Ukrainian President Petro Poroshenko. Three parties that are part of the majority coalition in parliament, however, opposed the constitutional changes.

"This is not a road to peace and not a road to decentralization," said the leader of one of those parties, former Prime Minister Yulia Tymoshenko. "This is the diametrically opposite process, which will lead to the loss of new territories."

Parliament speaker Vladimir Groisman denied that the changes would lead to the loss of the Donetsk region, where there have been clashes with separatists. "There is no hint of federalism. Ukraine was, is and will be a unified state," Groisman said.

A final vote on the constitutional changes is to be held during parliament's fall session, which begins on Tuesday. No specific date has yet been set.

Karmanau reported from Minsk, Belarus.