Two Ukrainian security officers were killed in the country's war-torn east, Kiev said Monday, a week before a crucial summit aimed at ending more than five years of conflict.

Unidentified explosive devices detonated, killing the men, as a group of Russian-backed separatists tried to break through enemy lines, the Ukrainian armed forces said.

The army said the combatants died at the scene.

Ukraine's SBU security service identified the troops as its officers, who were fighting alongside Ukraine's military against the pro-Russian insurgency in the east.

Ukrainian President Volodymyr Zelensky expressed his condolences to the families of the deceased.

"We will definitely achieve a ceasefire," Zelensky wrote on Facebook.

More than 13,000 people have been killed in the violence since April 2014 when the separatists declared two "people's republics" in the eastern Donetsk and Lugansk regions
More than 13,000 people have been killed in the violence since April 2014 when the separatists declared two "people's republics" in the eastern Donetsk and Lugansk regions AFP / Aleksey Filippov

"This will be the end of children's tears, mothers' pain and loss of our brothers."

The casualties came as Zelensky plans to meet Russian President Vladimir Putin during a four-way summit in Paris next week that is aimed at ending the war with the separatists, who have carved out breakaway statelets.

The two leaders will join French President Emmanuel Macron and German Chancellor Angela Merkel on December 9 for a summit that is expected to help find ways to end the stalled conflict.

More than 13,000 people have been killed in the violence since April 2014 when the separatists declared two "people's republics" in the eastern Donetsk and Lugansk regions.

Ukraine and its Western allies accuse Moscow of giving financial and military backing to the separatists, which Russia denies despite evidence to the contrary.

A series of truce agreements, brokered by France and Germany, have helped dampen hostilities but sporadic and sometimes serious clashes continue.