Crowds of protesters came to oppose amendments to the constitution that would provide for decentralization of the country.

The Interior Ministry confirmed at least 10 troops had sustained injuries in the blast, saying some officers were seriously wounded.

“A combat grenade has been thrown at the Ukrainian special forces. Some of the servicemen from [Ukraine] National Guard have been seriously injured. Their life is in danger,” Anton Gerashchenko, an adviser to Kiev’s Interior Ministry, wrote on his Facebook page.

The Ukrainian National Guard said on Facebook at least twenty of its servicemen have been injured in the clashes in Kiev. Other sources put the number of those injured at 30.

Tweets from journalists at the scene said supporters of the radical group Right Sector were brutally attacking police officers.

The demonstrators attacked police with long sticks and threw at least one smoke bomb grenade, Russia’s RIA Novosti and TASS news agencies reported.

The Ukrainian UNIAN news agency also reported that smoke bombs were being thrown along with stones. Police are now trying to stop the demonstrators from storming the parliament building.

Both protesters and police officers are using tear gas against each other, UNIAN said.

The agency added that the protesters are reportedly shouting “Shame!” and “Impeachment!” in front of the parliament building, which is currently blocked from the outside.

At least one protester has been detained, the Ukrainian Interior Ministry said in a statement.

A live feed by ‘112 Ukraina’ news channel also showed several police officers were injured in the clashes.

Earlier in the day, the parliament passed amendments to the Constitution on decentralization in the first reading. The amendments proposed by President Petro Poroshenko were supported by 265 of the parliament’s 450 lawmakers.

The lawmakers did not discuss giving a special status to Donbass, a historical area in eastern Ukraine that includes the Donetsk and Lugansk regions. Since April 2014 the area has been fought over by pro-Kiev and anti-government forces.

Despite the special status for the war-torn areas being a separate bill, the protesters who came out in the capital Monday were angered by the prospect of Eastern Ukraine getting autonomy from the central government. Photos posted on social media showed people holding banners saying, “No to special status of Donbass,” and “Occupants in Donbass, go away.”

The protesters on Constitution Square in Kiev are from the right-wing Radical, Self-Help, Svoboda (Freedom) and Republican Platform parties. TASS news agency has estimated their number to be around 1,000.

Inside the parliament, members of the Radical party attempted to block the tribune as the debate got under way. The disruption was led by the leader of the Radical Party, Oleg Lyashko.

Lyashko, along with his fellow party member Igor Mosiychuk, have recently been accused of organizing a criminal group, kidnappings and torture. On Saturday, Ukraine’s prosecutor general opened a case against the two right-wing politicians.

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