Clashes between the forces of Azerbaijan and Armenian-backed Nagorno-Karabakh have left several soldiers dead, with both sides blaming the other for the violence.
Azerbaijan's defence ministry said three Armenians and two Azeris were killed following an Armenian attack.
Armenian reports said one Armenian was wounded repelling Azeri forces, and up to seven Azeris were wounded or killed.
Recent attempts to solve the "frozen conflict" have failed to gather steam.
There have been a number of skirmishes in recent months across the ceasefire line dating to the 1990s.
Fighting broke out in the late 1980s as the Soviet Union headed towards collapse, with ethnic Armenians taking control of Nagorno-Karabakh and a land corridor linking it to Armenia.
Negotiations between the two countries, under a fresh peace drive backed by the US and Russia, took place last year but have since stalled.