Ukraine president vows to act over army deaths
Ukrainian President Petro Poroshenko has said his forces will find and destroy pro-Russian separatists in the east who killed more than 20 soldiers in a single attack.
The soldiers were killed in an apparent rocket strike near the Russian border.
Officials in Kiev say the separatists used Grad missiles.
They say that that more than 90 other soldiers were wounded in the most deadly attack since the president ended a unilateral ceasefire last month.
"For every life of our soldiers, the militants will pay with tens and hundreds of their own," President Poroshenko said.
"Not one terrorist will evade responsibility. Everybody will get what is coming to them," he said in a statement posted on his website after an emergency meeting of security chiefs.
Ukrainian officials say the rebels fired a barrage of Grad rockets at troops in Zelenopillya, a village near the border.
Pro-Russian rebels say they "destroyed a column" of troops there.
Russian-made Grad rockets are heavy artillery weapons fired in batches from lorries. Both the Russian and Ukrainian armed forces use them.
On Thursday night the rebels shelled Ukrainian troops at Donetsk airport.
The rebels have regrouped in Donetsk as the Ukrainian military has retaken territory in the country's east. The rebels have not yet broken through to the airport.
A motorised brigade from Lviv, western Ukraine, was targeted in the rocket attack, the Ukrainian news website Unian reports.
Beatings and torture
Meanwhile, a report by the human rights group Amnesty International has accused separatists of abuses in the three-month conflict.
The group said it had found "graphic and compelling evidence of savage beatings and other torture" by pro-Russian groups in eastern Ukraine.
The Amnesty report, Abductions and Torture in Eastern Ukraine, said that protesters and journalists had been targeted, and hundreds of people had been abducted.
Pro-government forces had also committed a smaller number of abuses, Amnesty said.