Pro-Russian rebels shelled government troops encircled in east Ukraine on Tuesday 17 February and a plan for both sides to pull back their heavy guns stalled, pushing a fragile peace deal closer to collapse.
One witness near the front line said artillery rounds rocked the town of Debaltseve every five seconds and black smoke rose skywards, despite a truce that has eased fighting in many areas since the European-brokered deal took effect on Sunday.
The rebels said they had captured parts of Debaltseve, which sits on a strategic railway junction, and that some Ukrainian soldiers had surrendered, a claim Kiev denied.
A Ukrainian soldier said the road to Debaltseve was under army control.
Hopes that the deal reached last week would end a conflict that has killed more than 5,000 people were always low after a rebel advance in January scuppered an earlier truce.
Smoke hung over Debaltseve, which has a peacetime population of about 25,000 and has been under fire for weeks.
Monitors from the OSCE security group were expected to try to reach the besieged town after Germany said it had agreed steps with the leaders of Russia and Ukraine to ensure they had "free access" in the east.
But a new call by Berlin for peace and for the withdrawal of heavy weapons to start as scheduled on Tuesday under the peace deal, fell largely on deaf ears.