At least five troops have been killed and four injured in eastern Ukraine in the past 24 hours in what appears to be the worst outburst of violence in months.

Fighting between Russia-backed separatists and Ukrainian government troops has killed more than 10,000 people since it began in 2014. A cease-fire deal signed in 2015 helped to reduce the scale of fighting but did not stop it altogether.

The press office of the Ukrainian armed forces said in a statement Friday four out of the five troops killed in the past 24 hours died outside the village of Krymske in the Luhansk region where the fighting lasted for eight hours. The Ukrainian government called it the biggest loss of life since July.

Luhansk rebels did not immediately report any casualties.