Fighting intensified in eastern Ukraine on Saturday as separatist rebels tried to seize more territory before a ceasefire takes effect at midnight, the Ukrainian military said.
The truce envisages the creation of a neutral "buffer zone" and withdrawal of heavy weapons responsible for many of the 5,000 casualties in a conflict that began almost a year ago and gave rise to the worst crisis in relations between Russia and the West since the Cold War a generation ago.
"Ahead of midnight, rebels are trying to complete tactically important plans to enlarge the territory under their control, primarily in the direction of Debaltseve," spokesman Andriy Lysenko said at a daily televised briefing in Kiev.
Debaltseve, a strategic transport hub northeast of the rebel-controlled stronghold city of Donetsk, has been the focus of some of the fiercest fighting in recent weeks.
Heavy shelling could be heard at a rebel checkpoint 10 km (six miles) from the Debaltseve, a Reuters witness said, reporting outgoing artillery rounds almost every minute.
A column of new military vehicles and artillery passed through the checkpoint in the direction of Debaltseve. The checkpoint was manned by several dozen, professional-looking combatants. Tanks and armored vehicles could also be seen.
Speaking on condition of anonymity, a rebel at the checkpoint said local fighters were being supported by "guests from Russia."
Spokesman Lysenko said separatist forces continued to be reinforced by fighters and military equipment crossing Ukraine's eastern border from Russia over the past 24 hours. Moscow denies bolstering the separatists with armor and troops although Western officials cite overwhelming evidence to the contrary.
REGIONAL AUTONOMY PART OF DEAL
The rebels have advanced far past the line of an earlier ceasefire deal, agreed in September, and the new accord appears to envisage them withdrawing their guns around 75 km, to take them back behind it, while Ukrainian guns would move 25 km back.
Thursday's four-power accord also prescribed constitutional reform to give eastern Ukraine, where many Russian speakers live, more autonomy. Kiev has made clear it rejects independence for the "People's Republics" the rebels have declared.
Tatyana Demchenko, deputy commander of the rebel unit in the town of Horlivka, said she had little faith the ceasefire would hold. "They'll shoot at us and we have to remain silent? Militias may receive the order not to open fire, but what - we sit and die in shelling? If they don't shoot, we won't," she said, holding two grenades in her hands.
Ukrainian President Petro Poroshenko said the country had reached an important crossroads between war and peace.
"Either the enemy stops shooting and embarks on de-escalation ...or the enemy escalates the conflict for us and for Europe and the whole world," he said at a ceremony for border guards shown on television.
Seven Ukrainian service personnel have been killed and 23 wounded in fighting in the past 24 hours, Lysenko said.
The Group of Seven industrialized countries issued a statement late on Friday calling on all sides to refrain from actions that would hinder the start of the ceasefire. It said G7 countries were ready to take "appropriate measures" against those who violate the agreement, an apparent threat of more punitive economic sanctions against Russia shortly.
The deal, sealed by the leaders of Germany and France after 16 hours of all-night talks in Minsk, capital of Belarus, with the Russian and Ukrainian presidents, was quickly overshadowed by escalating bloodshed on the ground.