"In the past day, we lost six soldiers. Another 13 were wounded," Ukrainian National Security and Defence Council spokesman Andriy Lysenko told reporters.
The toll was one of the highest reported by the Ukrainian armed forces in recent weeks.
Ukrainian President Petro Poroshenko and the separatist leaders of the pro-Russian regions of Lugansk and Donetsk yesterday said they had reached a deal to halt fire in their eight-month conflict on December 9.
But that local truce has been repeatedly broken and it remains uncertain whether the deal announced for next Tuesday will hold.
The United Nations believes that the war has killed more than 4,300 people and driven nearly one million from their homes.
