The incident, which occurred in the Mardakert district in the northwest of Nagorno-Karabakh region, is a "fairly serious encroachment," Armenian Foreign Minister Vartan Oskanyan was quoted as saying.
"This is different from a usual violation of the ceasefire regime" adopted by the two sides in 1994, he said.
The territory of Nagorno-Karabakh is a region in Azerbaijan populated mostly by ethnic Armenians.
No immediate comments are available from Azerbaijan so far.
Armed conflict broke out in the early 1990s between Azerbaijan and Armenia over the region's status after it declared independence, which was not recognized by the international community.
A Russian-brokered ceasefire halted the fighting in 1994, but the dispute remains unsolved.
Güncelleme Tarihi: 05 Mart 2008, 12:29