Ukraine's military says that five of its soldiers have been killed and four wounded in clashes with Russia-backed separatists in the east of the country.
The military said in a November 24 statement that four of the soldiers were killed in a gunfight the previous day near the village of Krymske that lasted around eight hours.
Krymske lies around 30 kilometers west of Luhansk, where tensions have escalated this week between separatist factions that control the city.
A total of four Ukrainian soldiers were wounded in clashes with separatists on November 23, the military said. It said eight separatists were killed and nine were injured.
"Five of our soldiers have died over the past 24 hours," Oleksandr Turchynov, chief of the National Security and Defense Council, said in televised remarks on November 24. "It is a very serious problem for us."
He added that "a conflict situation is under way between various criminal groups that make up the occupational administration on the occupied territories."
Fighting between Kyiv's forces and the Russia-backed separatists who hold parts of the Donetsk and Luhansk regions has killed more than 10,000 people since April 2014.
Moscow denies involvement in the conflict, despite compelling evidence to the contrary. Moscow also says it respects Ukraine's territorial integrity although it annexed the Ukrainian region of Crimea in March 2014 and controls part of Ukraine's border over Kyiv's objections.
Several cease-fire deals announced as part of the Minsk accords -- September 2014 and February 2015 pacts aimed to resolve the conflict -- have failed to hold.
The latest cease-fire was agreed on August 22 in a phone call between the leaders of Germany, France, Russia, and Ukraine. Kyiv and the separatists regularly trade accusations of cease-fire violations.
The spike in violence overnight comes amid an apparent power struggle among Russia-backed separatists in Luhansk. Rumors have swirled for days that the separatist leader in the region, Igor Plotnitsky, has fled to Russia.
Plotnitsky had previously fired the region's so-called interior minister, Igor Kornet, and then accused him of organizing a coup against the separatist leadership.
Kremlin spokesman Dmitry Peskov said on November 22 that Russia was closely following the situation in Luhansk, where armed men in unmarked uniforms have taken up positions in recent days.
But Peskov declined to comment on Plotnitsky's whereabouts on November 24, saying that "this is not an issue that the presidential administration deals with," Russia's state-run TASS news agency reported.