“Ukrainian military casualties over the last 24 hours are 40 dead, 50 injured,” Eduard Basurin said.
He added that several pieces of Ukraine's military equipment had also been destroyed, including a tank, two infantry fighting vehicles, three armored personnel carriers, and three mortars.
Sporadic clashes have been reported across eastern Ukraine by both conflicting parties since the ceasefire deal was agreed upon in Belarus last week.
Roughly 3,000 Ukrainian troops had been killed in the fight for Debaltsevo, a strategic transport hub, Denis Pushilin said earlier on Thursday as quoted by Russkaya Sluzhba news agency.
The peace agreement is broadly observed elsewhere, with militias already withdrawing heavy artillery from the line of the conflict.
The armed conflict has killed around 5,600 civilians since the Ukrainian government launched a large-scale military operation in the southeast last April.