The defense ministry of the separatist Nagorno-Karabakh region said three of its soldiers were killed and another four were wounded Thursday while repelling an Azerbaijani incursion.

It said an unspecified number of Azerbaijani invaders were killed during the clash, which lasted about two hours. Azerbaijan's Defense Ministry, in turn, blamed the Armenian side for the clash and claimed that 20 Armenian soldiers were killed or wounded. The conflicting claims couldn't be independently verified.

Azerbaijan's Nagorno-Karabakh region and some adjacent territory have been under the control of Armenian soldiers and local ethnic Armenian forces since a 1994 cease-fire that ended a six-year war.

Attempts to negotiate a peaceful settlement have stalled, and the sides engage in frequent shootings along the buffer zone.

Armenian and Azerbaijani officials have exchanged tough statements, blaming each other for provocative actions.

Armenian President Serge Sarkisian said Wednesday that "attempts to speak to Armenia and Nagorno-Karabakh in the language of threats, provocations and blackmail will not lead to settlement of the problem."

In Azerbaijan's military statement issued Thursday, Defense Minister Zakir Gasanov was quoted as saying that "all enemy provocations on the line of contact will be harshly stopped."