KIEV, Nov. 15 - President Petro Poroshenko on Sunday decried a sudden re-escalation in the conflict with pro-Russian separatists after a Ukrainian soldier was killed in clashes in the country's east, AFP reported.

Fighting has intensified in recent days with six soldiers killed over the weekend despite a September truce agreement.

On Saturday, Ukraine had reported the death of five soldiers, the highest military death toll since the beginning of the 10-week truce. Sunday's assault saw separatists near Donetsk airport also injure eight soldiers.

"We see there is a net escalation in the conflict in the east (amid) a rise in the number of (separatist rebel) attacks," Poroshenko told Ukrainian television.

"I have given orders to open fire in response as soon as our troops' lives come under threat," Poroshenko warned.

Ukrainian army spokesman Oleksandr Motuzyanyk indicated that "the enemy cynically fired 122mm caliber mortars on Ukrainian positions near to Avdiyivka."

The locality has been under Ukrainian control in an area which saw fierce fighting before falling to the separatists last January.

He added the Ukrainians had come under fire 37 times inside 24 hours, including Sunday's shelling some 10 kilometers (six miles) north of the de facto rebel capital Donetsk.

The developments come a week after international monitors in eastern Ukraine have reported a sharp increase in gunfire along front lines near the airport of the rebel-held city of Donetsk.

The guns have been mostly silent since early September, prompting both sides to extend a pullback of lighter weapons, but recent accusations of ceasefire violations from both sides have underscored the fragility of the peace process.

Renewed violence also makes it less likely that the European Union lifts sanctions against Russia based on a review before the end of the year, though Russia has repeatedly denied it is backing the rebels in east Ukraine.

The Organization for Security and Cooperation in Europe (OSCE), which monitors the implementation of the ceasefire agreement, said it had noted violations near Donetsk airport, a long-time hotspot for fighting.

After the September truce, fighting dipped to its lowest level since the start of the 19-month conflict. But a recent uptick in violence has sparked concerns it could unravel.

More than 8,000 people have been killed since insurgents took up arms against Ukraine's pro-Western government last year following the ousting of a pro-Russian president in the capital Kiev. (afp/ez)