Three Ukrainian servicemen have been killed and 12 wounded in the latest clashes between government forces and Russian-backed separatists, further eroding a three-month-old ceasefire, Kiev's military said on Friday.
Military spokesman Andriy Lysenko said government forces had come under attack from separatists using large-calibre guns and mortar in several parts of the east and southeast, including near the rebel-controlled city of Donetsk.
"In the past 24 hours we have lost three Ukrainian heroes, and another 12 have been wounded," Lysenko told a briefing.
There was no word on casualties among the separatists, who Kiev, NATO and Western countries say are being provided with arms and men by Russia, something Moscow denies.
Ukraine's largest steel company, Metinvest, said one worker had been killed and two wounded when its Avdiyivka coke plant, which is on government-controlled territory, was been hit by heavy shelling on Thursday.
The plant is not able to receive supplies of raw materials or ship out finished products, and damage to equipment has further hampered production, Metinvest said in a statement.
A surge in violence is putting further pressure on a fragile ceasefire brokered by Russia, Germany and France in a peace deal last February in Minsk, Belarus.
Lysenko said there had been intense fighting near Gorlivka, north of Donetsk, with the separatists using "a significant quantity" of mortars against government forces.
But the heaviest casualties on the government side had been sustained near Donetsk itself. The separatists were using "a broad range of weapons" against Kiev's forces at Shyrokyne, to the east of the strategic port city of Mariupol on the Sea of Azov, he said.
More than 6,200 people have been killed since the conflict erupted in April 2014 after the ousting of a Moscow-backed president by street protests and the arrival in power of a leadership dedicated to moving Ukraine away from Moscow's orbit towards integration in Europe.
The conflict has led to the biggest crisis in Russia-West relations since the end of the Cold War.
In a report released on Friday, Amnesty International said there was "overwhelming evidence" that both Ukrainian forces and pro-Kiev militias and separatist groups had mistreated or tortured prisoners — abuse it described as "frequent and widespread."
"Prisoners described being beaten until their bones broke, tortured with electric shocks, kicked, stabbed, and hung from the ceiling, deprived of sleep for days, threatened with death, denied medical care, and subjected to mock executions," the report said.
It highlighted Right Sector, a militant Ukrainian nationalist group, and various semi-autonomous separatist battalions as being especially brutal to prisoners.