Ukraine has appealed to the West to get tough on Russia after separatists it says are militarily backed by Moscow stormed a flashpoint town to attack thousands of troops in violation of a three-day-old ceasefire.
As EU and UN officials expressed concern at the violence in the town of Debaltseve, Russian President Vladimir Putin - who denies having a hand in Ukraine's insurgency - urged Kiev to permit its beleaguered soldiers to surrender.
"I hope that the Ukrainian authorities are not going to prevent the Ukrainian soldiers from laying down their weapons," Putin said in a press conference during a visit to Budapest.
He also said the 10-month Ukrainian conflict, which has so far killed more than 5600 people, could not be solved by "military means".
Ukrainian President Petro Poroshenko, in a phone conversation with German Chancellor Angela Merkel, said the assault on Debaltseve, a strategic rail hub in the country's east, was a "cynical attack" on the truce brokered last week by Germany and France.
He called for the European Union and international community to take a "tough reaction against the treacherous actions of the rebels and Russia".
The comments came just ahead of a UN Security Council meeting that adopted a Russian-sponsored resolution calling for an immediate end to hostilities in Ukraine and compliance with the ceasefire.
Intense shelling was heard in the Debaltseve area on Tuesday.
Ukrainian officials admitted that the pro-Russian rebels attacking Debaltseve had taken parts of the town and surrounded some of the army units there, but said fierce fighting was continuing.
"The hopes of the world for peace are being destroyed," the deputy head of Ukraine's presidential administration, Valeriy Chaly, said.
Rebels claimed to control 80 per cent of Debaltseve and to have killed "many" of the 8000 soldiers they have said were holed up in the surrounded town, and taken scores others prisoner.
An estimated 5000 civilians were also cowering in cellars, with little water or food.
It was not known how many casualties the street-to-street combat by fighters armed with automatic weapons and grenade launchers had caused.
Journalists and observers from the Organisation for Security and Cooperation in Europe (OSCE) have been stopped by rebels from entering the town.
A man casts a shadow on a wall where pictures of victims of the Maidan Square protests are placed in Kiev, Ukraine. Photo / AP
The insurgents had waged an intense bombardment of the town last Saturday, the day before the ceasefire came into effect, and kept up rocket and mortar fire afterwards.
That violence, and other breaches of the truce both sides blamed on the other, prevented the warring forces from pulling back heavy weapons from the frontline in Ukraine's east as was meant to happen from Tuesday.
The pro-Russian rebels have since argued that Debaltseve was well inside their territory and so should not be included in the ceasefire agreement.
But Ukraine described it as a finger of territory it controlled and therefore subject to the truce.
