KIEV: Russia-backed separatists in Ukraine's war-torn east have reported four of their troops killed and five more injured as the years-long conflict continues to simmer.

The new casualties come just days after Russian leader Vladimir Putin and US President Joe Biden held their first summit meeting in Geneva last week.

The years-long conflict in eastern Ukraine -- including an escalation of tensions since the start of 2021 -- was on the agenda, but no agreements were announced.

Officials in the self-proclaimed Donetsk People's Republic said Monday evening that three of their troops were killed by the Ukrainian army and one wounded in mortar fire in the village of Lozove, close to the separatists' de facto capital Donetsk.

The separatist mouthpiece, DAN news agency, said one more fighter was killed and four were wounded hours later, when an ambulance car was hit by a grenade launcher while evacuating the injured.

In a statement, top Donetsk official Denys Pushilin said the separatists would take "retaliatory steps" following the incident.

Kiev rejected the claim.

Citing intelligence, the Ukrainian military said in a statement that the separatist troops died as a result of "detonating their own explosive devices and the careless handling of weapons".

Kiev has been battling Russian-backed separatists in the eastern Donetsk and Lugansk regions since 2014, following Moscow's annexation of the Crimean peninsula.

The war has claimed more than 13,000 lives.

After a lull last year, fighting escalated at the start of 2021 and in April Russia amassed 100,000 troops near the Ukrainian border and in Crimea, prompting warnings from NATO.

Although Russia later announced a pullback, both Washington and Kiev said the withdrawal has been limited.

Kiev and its Western allies accuse Russia of sending troops and arms to support the separatists, which Moscow has denied.