Two people were killed and about eight others injured in a bomb explosion at a march Sunday in Ukraine's second-largest city that was commemorating the first anniversary of the ouster of president Viktor Yanukovych, the country's interior ministry said.
The Interior Ministry said the blast was due to an "unknown explosive device" and was being considered a terrorist act.
The violence comes as Ukraine continues to be riven by tension and bloodshed stemming from Yanukovych's fall a year ago. The Ukrainian parliament voted Feb. 22, 2014 to remove the Russia-friendly president, following months of increasingly violent protests in the capital, Kiev.
The Crimean peninsula, where residents largely regarded his downfall as a coup, was annexed by Russia a month later. Then armed rebels opposed to the new authorities in Kiev took over large parts of two regions bordering Russia, setting off a war that has killed more than 5,600 people.
A peace plan envisioning a cease-fire and pullback of heavy weapons was signed 10 days ago, but cease-fire violations continue.
Ukraine plans to begin pulling back heavy weaponry from the front lines on Sunday in accordance with the peace plan, a military spokesman said. Ukrainian military spokesman Col. Andriy Lysenko told a briefing that the withdrawal was to begin, but did not give further details.
Rebel spokesman Eduard Basurin said the pullback from both sides is to take place between Sunday and March 7, but he did not specify whether rebels had made any moves yet. There was no immediate confirmation that the withdrawal had begun.
Both sides are to pull back their big guns and rockets from 25 to 70 kilometers (15 to 43 miles) away from the conflict line -- depending on the weapons' size -- creating a buffer zone of between 50 and 140 kilometers (31-87 miles).
The buffer zone was a main element of a peace agreement worked out in marathon negotiations 10 days ago in Minsk, Belarus. It also calls for a full exchange of war captives.
Late Saturday, 139 Ukrainian soldiers and 52 rebels were exchanged; it remains unclear how many prisoners in total are on each side and when other swaps might take place.
The cease-fire that was the first element of the Minsk plan was called into effect last Sunday.
Ukraine said Russia-backed separatists violated the cease-fire a dozen times during the night with artillery and rocket attacks and an attempt to storm a Ukrainian encampment.
Lysenko said one serviceman was killed and three wounded over the past day.
