Officials in the disputed territory of Nagorno-Karabakh accuse Azerbaijan of attacks that have left three ethnic Armenian soldiers dead.
The Nagorno-Karabakh de-facto Defense Ministry said Azerbaijani commandos attacked its soldiers' position on March 19, killing three soldiers and wounding four.
Meanwhile, Azerbaijan's Defense Ministry accused separatists of triggering the confrontation and said 20 Armenian soldiers had been killed or wounded.
Armenia warned Azerbaijan it would not stand by if Nagorno-Karabakh was attacked.
Baku and Yerevan have been locked in a conflict over Azerbaijan's breakaway region of Nagorno-Karabakh for nearly 25 years.
Armenia-backed separatists seized the mainly ethnic Armenian-populated region during a war in the early 1990s that killed some 30,000 people.
International diplomatic efforts to settle the conflict have brought little progress.