Armenia has said at least 49 of its soldiers have been killed as clashes broke out with Azerbaijan.
The escalation of hostilities between the south Caucasus countries has fuelled fears a fully-fledged war could break out between the former Soviet nations.
Armenia said several towns near the border with Azerbaijan had been shelled in the early hours of Tuesday morning.
It said it had responded to a “large-scale provocation” by Azerbaijan.
Armenian Prime Minister Nikol Pashinyan accused Azerbaijan of attacking Armenian towns because it did not want to negotiate over the status of Nagorno-Karabakh, an enclave inside Azerbaijan which is mainly populated by ethnic Armenians.
“The intensity of hostilities has decreased but attacks on one or two fronts from Azerbaijan continue,” Mr Pashinyan said in a speech to parliament, according to Russian media.
He said it came after recent European Union-backed talks in Brussels with Azerbaijan’s President Ilham Aliyev, which revealed what he said was Azerbaijan’s uncompromising stand.
Meanwhile Azerbaijan said it was attacked by Armenia.
It said Armenian forces had been engaged in intelligence activity on its border, moved weapons into the area and had planted mines.
Russia, which has around 2,000 soldiers deployed in the region as part of a previous peace deal, moved quickly to broker a ceasefire.
It follows a decades-old rift between the neighbouring countries.
Armenia is a land-locked country on the eastern border of Turkey which borders Azerbaijan to the west, while Azerbaijan borders the Caspian Sea on its east side.
Conflict first began in the 1980’s when both countries were part of the Soviet Union.
Armenian forces captured territory near Nagorno-Karabkah, which Azerbaijan later partially regained in 2020 in fighting that lasted six weeks and killed over 6,600 people.
The conflict ended with a Russian-brokered truce and thousands of residents returned to the homes they had fled.
Both Russia and Europe have called on the nations to observe restraint.
The Russian foreign ministry said the latest conflict “should be resolved exclusively through political and diplomatic means”.
Charles Mischel, president of the European Council, also urged Mr Pasyhinyan to prevent further escalation.
