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Long-simmering tensions between Armenia and Azerbaijan appear to have flared up in the contested Nagorno-Karabakh region, with both sides accusing each other of attacking civilians amid reports of casualties.
The neighboring former Soviet republics have long been at odds over the territory -- which is situated within the borders of Azerbaijan -- and fought a war over it that finished in 1994.
Despite the conflict ending with a Russian-brokered ceasefire, military skirmishes between the two sides are not uncommon.
While Armenia said it was responding to missile attacks launched by its neighbor Sunday, Azerbaijan blamed Armenia for the clashes.
In response to the alleged firing of projectiles by Azerbaijan, Armenian Prime Minister Nikol Pashinyan tweeted that his country had "shot down 2 helicopters & 3 UAVs, destroyed 3 tanks."
As a result of the escalating tensions, the Armenian government has decided to impose martial law and to order "general mobilization," Pashinyan said in a later tweet.
Armenia earlier claimed that its neighbor had targeted civilians in peaceful areas, including in the region's capital Stepanakert.
Artak Beglaryan, an official from the self-proclaimed Republic of Artsakh, a de facto independent Armenian state not recognized internationally and which controls the region of Nagorno-Karabakh, said in a tweet that a mother and child had been killed.