Mariupol: Ukraine accused pro-Russian rebels of waging fresh attacks in the restive east on Monday, further imperilling a fragile truce as EU leaders prepared to approve punishing new sanctions on Moscow.
Russia warned it would retaliate against the new measures, which the EU has nevertheless said could be suspended if Moscow observes the ceasefire deal and removes its troops from Ukraine.
The warring parties have each accused the other of breaching the pact since it was signed Friday, the first backed by both Kiev and Moscow to end a conflict that has plunged East-West relations to a post-Cold War low.
Ukrainian soldiers were strengthening their positions around the flashpoint port city of Mariupol after weekend shelling by the insurgents left one woman dead.
"Despite the ceasefire, Ukrainian positions are still coming under attack," said Ukrainian defence spokesman Andriy, also accusing Russian troops of stirring trouble.
"Russian sabotage and reconnaissance forces are attacking the terrorists' positions under the guise of being Ukrainian servicemen," he said.
Ukrainian forces said separatist militias had violated the truce overnight in Mariupol, which remains in government hands despite a rebel advance, and in the eastern insurgent strongholds of Lugansk and Donetsk.
The first attacks outside Mariupol late Saturday erupted only hours after Ukrainian President Petro Poroshenko and Russian leader Vladimir Putin issued nearly identical statements agreeing the truce was "generally holding" and vowing to pursue further steps toward peace.
Western governments accused Moscow of sending in huge numbers of troops and heavy weapons to back insurgents who launched a counter-offensive across the southeast in late August in a devastating reversal of fortune for the Ukrainian military.
Mariupol has emerged as a key battleground with the insurgents apparently set on creating a land corridor between the Russian border and the Crimean peninsula annexed by Moscow in March.
Russia has repeatedly dismissed the claims as propaganda but Western leaders, deeply suspicious of Moscow's territorial ambitions, have reacted by threatening new sanctions and boosting its military presence in eastern Europe.
In a further show of force, NATO and Ukraine launched naval drills in the Black Sea today. Ahead of annual ground exercises next week.
EU President Herman Van Rompuy said the new sanctions due to be approved today could be reviewed if the ceasefire proves "durable".