Armenia’s Prime Minister on Sunday called on citizens to ‘defend our sacred homeland’ after heavy fighting with Azerbaijan brought the arch enemies to the brink of all-out war.
The clashes erupted on Sunday morning in the separatist region of Nagorno-Karabkh, an ethnically Armenian zone within the official borders of Azerbaijan but outside of its control.
Tensions have been rising for months over the disputed territory, which was seized by Armenian separatists in 1991 in one of the bloodiest wars that followed the collapse of the Soviet Union.
Both sides, former members of the Soviet bloc, on Sunday denied being the aggressor, while reporting 24 military and civilian casualties that included at least one child.
Russia has a military base in Armenia and a fully-fledged war could draw it into conflict with Turkey, the other key power in the region, which backs Azerbaijan.
In an attempt to prevent a major conflagration, Moscow called for a ceasefire and negotiations, along with France, Germany and the EU.
Ankara blamed Armenia for "hostility that will send the region into fire" and offered Baku its full support.
At just past 8am local time, Azerbaijan launched an air and artillery offensive in Nagorno-Karabakh, according to Armenia's defence ministry.
In response, the army downed four Azerbaijani helicopters and 15 drones.
Officials in Nagorno-Karabakh said that 16 of the breakaway region's soldiers were killed in fighting with Azerbaijani troops, with a further 100 wounded.
They said Azerbaijan was bombing the front-line including the main city of Stepanakert. A woman and a child were killed, according to Armenian rights activists.
Azerbaijan instead claimed it began a "counter-offensive" in the region "to protect the population" after Armenian shelling violated a cease-fire agreement.
Azeri forces had captured seven villages in the fighting, the defence ministry claimed, though that was denied by Yerevan, the Armenian capital
In a televised address to the nation following the clashes, Azerbaijan President Ilham Aliyev vowed victory over Armenian forces.
“Our cause is just and we will win,” Aliyev said, repeating a famous quote from Soviet dictator Joseph Stalin's address at the outbreak of World War II in Russia.
“Karabakh is Azerbaijan,” he said.
Armenia on Sunday declared martial law and mobilised its male population, with prime minister Nikol Pashinyan telling citizens to “get ready to defend our sacred homeland” in a Facebook post.
Nagorno-Karabakh announced the same steps.
The South Caucasus, where the fighting is taking place, is a corridor for pipelines transporting oil and gas to world markets.
According to the Turkish defence ministry, the Russian and Turkish defence ministers discussed the clashes over the phone on Sunday.
Russia announced "snap combat drills" in Armenia in July, following a smaller flare up on the Armenia-Azerbaijan border - hundreds of miles from Nagorno-Karabkh - in which at least 17 soldiers from both sides were killed.
Turkey also launched “large-scale Turkish-Azerbaijani military exercises” at the time, according to the Atlantic Council.
France, Russia and the United States have previously shepherded peace negotiations in the region as the "Minsk group", but the last push for a deal collapsed in 2010.
The European Union called Sunday for a halt to fighting and an “immediate return to negotiations”.
Political observers said global powers should intensify talks to stop the conflict.
"We are a step away from a large-scale war," Olesya Vartanyan of the International Crisis Group told AFP.
"One of the main reasons for the current escalation is a lack of any proactive international mediation between the sides for weeks," she added.