Ukraine's military on Saturday reported the death of two soldiers in the past day of fighting with pro-Russian insurgents in the separatist east.

Military spokesman Andriy Lysenko added that 20 soldiers were wounded in clashes in the mostly Russian-speaking Lugansk region.

The toll brings to six the number of Ukrainian troops reported killed since Thursday evening -- an escalation since the two warring sides agreed a new December 9 truce aimed at stemming fighting that has claimed some 4,700 lives.

The upsurge in violence comes ahead of talks that Ukrainian President Petro Poroshenko hopes to stage next week with Russia's Vladimir Putin at a mini-summit in Kazakhstan that would also be attended by the leaders of Germany and France.

German Chancellor Angela Merkel and French President Francois Hollande have indicated in the past few days that too little has been done to achieve a lasting ceasefire to make political dialogue worthwhile at this stage.