Azerbaijan has called planned military exercises by Armenian-backed forces in its breakaway region of Nagorno-Karabakh this week a "provocation" aimed at increasing tensions.
The de facto authorities in Nagorno-Karabakh said their air force will conduct military exercises on September 25-28 with the aim of improving pilot skills.
The announcement sparked fury in Baku, where the Defense Ministry warned that "any enemy aircraft that would attempt to approach the foremost positions of the units of the Azerbaijan Army will be immediately neutralized."
"All responsibility for possible losses will entirely rest with the military and political leadership of Armenia," a statement said.
A spokesman for the separatists said they would retaliate "if we feel a threat or any aggressive behavior from Azerbaijan."
Azerbaijan and Armenia have been locked in a conflict over Nagorno-Karabakh for years.
The region, populated mainly by ethnic Armenians, declared independence from Azerbaijan amid a 1988-94 war that claimed an estimated 30,000 lives and displaced hundreds of thousands of people.
Internationally mediated negotiations with the involvement of the OSCE's so-called Minsk Group have failed to result in a resolution. The Minsk Group is co-chaired by France, Russia, and the United States.
Azerbaijan has accused Armenia's leadership of stoking tensions ahead of a planned meeting between the two countries' foreign ministers on the sidelines of the UN General Assembly in New York on September 26.
"We cannot exclude that the latest steps of Armenia's new prime minister are aimed at turning the situation into a military confrontation," Azerbaijani Foreign Minister Elmar Mammadyarov said on September 25.
Speaking at a meeting with ethnic Armenian businessmen in Moscow, Prime Minister Nikol Pashinian said on September 9 that he saw Karabakh as "part of Armenia" in the future.
Baku later said that the statement could damage international efforts to resolve the decades-long dispute over the region.