An explosion has killed two people and wounded 11 in Ukraine's government-controlled eastern city of Kharkiv, officials said.
The explosion happened during a pro-Ukrainian march marking the one-year anniversary of the overthrow of the country's former pro-Kremlin president.
A local official said two people died, one of them a police officer, revising down an earlier toll of three killed.
"It was a homemade bomb packed with shrapnel, put in a plastic bag and hidden in snow by the side of the road," he said.
Ukrainian security service adviser Markian Lubkivksi said on his Facebook page "people who might have been involved" in the attack had been arrested, without elaborating.
Kharkiv is located more than 200km from the frontline where pro-Russian rebels are fighting government forces.
Other marches celebrating the overthrow of former president Viktor Yanukovych a year ago, after street protests had been brutally repressed by snipers, were taking place in Kiev and other parts of Ukraine.
A UN-backed ceasefire came into effect in eastern Ukraine a week ago but yet to be fully implemented by both sides in the conflict.
Rebel forces begin weapon withdrawal
Earlier, a Russian general involved in implementing the ceasefire in eastern Ukraine said rebel forces will today begin withdrawing heavy weapons from the front line.
The two sides had agreed to start moving their artillery five days ago but, with heavy fighting continuing in some areas, had failed to do so.
The Ukrainian government has not yet responded to the latest announcement.
Last night there was also an exchange of more than 200 prisoners between Ukraine and pro Russian separatists.
Fighting has eased in many areas since a ceasefire came into effect last week, but the truce was shaken by the rebel capture of the town of Debaltseve on Wednesday, forcing a retreat by thousands of Ukrainian troops.
However moves towards pulling back heavy weapons, together with the exchange of dozens of prisoners with Ukrainian government forces on Saturday, could indicate the rebels intend to observe the truce more fully, having achieved a key military objective by seizing Debaltseve.
"The plan was signed last night ... Starting from today there are two weeks to withdraw heavy weapons," Interfax news agency quoted rebel commander Eduard Basurin as saying.
Russian news agency TASS quoted him as saying the pull-back was still being organised and that the actual withdrawal of weapons would take place from Tuesday.
Ukrainian military spokesman Andriy Lysenko said by telephone there was no confirmation yet as to whether the rebels had started pulling back their weapons.
A Reuters witness saw a 20-vehicle convoy of separatist military trucks with anti-aircraft missile systems and howitzers leaving Debaltseve in the direction of Donetsk.
The exchange of nearly 200 prisoners in Minsk yesterday was one of the first moves to implement the peace deal reached on 12 February between French, German, Russian and Ukrainian leaders.
Both sides continue to accuse each other of violating the ceasefire.
The Ukrainian military said rebels had launched 12 attacks on government troop positions overnight, using artillery and mortar fire.
The town of Pesky near Donetsk had seen the most intense fighting, while separatist groups had attempted to "storm" Ukrainian positions in Shyrokyne, east of the port city of Mariupol on the Sea of Azov, the military said on Facebook.
Kiev accuses the separatists of building up forces and weapons in Ukraine's southeast and has said it is braced for the possibility of a rebel attack on Mariupol.
The rebel press service DAN said Ukrainian troops had been shelling parts of Donetsk, reporting that artillery fire could be heard in the city early this morning.
