The number of people killed in clashes between protesters and police in Kiev, Ukraine's capital, has risen to three, according to the interior ministry.
Two more National Guard officers died on Tuesday from injuries sustained from a grenade blast during some of the worst violence the country has suffered since an uprising in early 2014.
Nationalist protesters and security forces had fought outside parliament on Monday, as politicians gave preliminary approval to a law to give greater powers to Russia-backed separatists in the east.
About 140 people, mostly security officers, were hospitalised because of the violence, which involved protesters from the far-right Svoboda party, the AP news agency reported.
About 30 protesters were detained, of whom 18 remained in custody on Tuesday, including the man suspected of throwing the grenade.
Ukrainian Interior Minister Arsen Avakov said the man was a Svoboda member who fought in the east in one of the volunteer battalions, which are loosely controlled by the government.
The decentralisation of power was a condition demanded by Moscow for a truce signed in Belarus in February aimed at ending the fighting between government troops and Russia-backed separatists that has left more than 6,800 people dead since April 2014.
But Ukrainian nationalists strongly oppose the constitutional changes, saying they would threaten the country's sovereignty and independence.
Poroshenko and his supporters insist that the constitutional amendment would devolve powers to local communities in all of Ukraine, from east to west, while making sure that the country remains a unitary state.
While nationalists think the amendment gives too much power to the regions, including the east, Russia-backed rebels there say it is not enough.
Speaking to Russian news agencies in Donetsk, rebel leader Alexander Zakharchenko criticized Poroshenko for taking out a clause that could offer sovereignty to the east, and make it a part of a loose confederation within Ukraine.
Now that 265 politicians have given it preliminary approval, the bill comes up for the final vote where Poroshenko will need to get at least 300 votes.
A truce in eastern Ukraine brokered by Western powers in February helped to subdue the fighting but did not stop it completely.
Source: Al Jazeera And AP