KIEV, Aug. 13 -- Dozens of pro-government troops were reportedly killed in fighting with independence-seeking insurgents in eastern Ukraine since Tuesday, according to media reports on Wednesday.

Eleven Ukrainian army soldiers were killed and 41 injured during a day and night of the heavy battles in Donetsk and Lugansk regions, said Andrei Lysenko, a spokesman for Ukraine's National Security and Defense Council (NSDC).

In a separate development, at least 12 pro-government fighters from the Ukrainian ultra-nationalist group Right Sector were reportedly killed when their convoy was ambushed by insurgents.

According to the Right Sector spokesman Artem Skoropadsky, the pro-Ukrainian fighters were travelling across the rebel-held area outside the city of Donetsk, when they came under attack by heavy gunfire.

The fate of over a dozen of other Right Sector fighters involved in the incident is unknown, Skoropadsky said, adding that the ambush was the bloodiest single fighting the ultra-nationalist group has ever had since clashes erupted in eastern Ukraine in mid-April.

Meanwhile, the representatives of the self-proclaimed "Donetsk People's Republic" (DNR) confirmed that they carried out the attack against pro-government forces, but gave different number of casualties.

According to the data published on the DNR page in the local social media, seven of Right Sector members were killed and 13 were injured during the ambush, while several fighters escaped the site.

The Right Sector is a radical nationalist group, a key participant of the recent protests in Kiev, which toppled the former authorities and is now fighting against insurgents in eastern Ukraine along with government forces.