"Six servicemen were wounded in an attack by Azerbaijani armed forces" in Karabakh's Nor Shen community, Armenia's rights ombudsman, Arman Tatoyan, said on Facebook, adding that two soldiers were in a critical condition.

The war for Nagorno-Karabakh last autumn claimed about 6,500 lives and saw Armenia cede territories it had controlled for decades, while Russia deployed peacekeepers in the area.

The region was also at the centre of a 1990s war that cost 30,000 lives during the death throes of the Soviet Union, when ethnic Armenian separatists broke away from Azerbaijan.

Since the latest conflict, both Azerbaijan and Armenia have reported occasional exchanges of fire along their shared border, sparking fears of another flare up in their territorial dispute.

"The presence of the Azerbaijani armed forces in the vicinity of Armenian civilian communities poses a serious threat to the security and peace of the civilian population; it is a violation of their right to life," Tatoyan added.

Karabakh's de facto foreign minister Davit Babayan told journalists the situation was calm after the incident and that it would "not provoke large-scale hostilities".

"A fresh war is impossible so long as Russian peacekeepers are deployed here," he said.

Azerbaijan's defence ministry denied any role in the incident saying "there was a shootout between illegal Armenian armed units".

On Thursday evening, Azerbaijan said one of its soldiers was killed in sniper fire by "illegal" Armenian forces.

News of that incident came as Armenia and Azerbaijan's foreign ministers were holding talks with Russia in Belarus on Thursday, aimed at mending ties.