At least 29 people have been killed in a second day of heavy clashes between Armenia and Azerbaijan following the fiercest flare-up of their conflict in more than a quarter of a century.
Forces from the ex-Soviet neighbours fired rockets and artillery at each other as fighting escalated on Monday around the disputed territory of Nagorno-Karabakh.
Any move to all-out war could drag in major regional powers, with Russia a defence ally of Armenia, and Azerbaijan backed by Turkey.
Crisis Group, an independent organisation which works to prevent wars, said “we haven’t seen anything like this since the ceasefire to the war in the 1990s”.
“The fighting is taking place along all sections of the front line,” said Olesya Vartanyan, a senior analyst at Crisis Group for the South Caucasus region.
“If there are mass casualties it will be extremely difficult to contain this fighting and we will definitely see a full-fledged war that will have a potential intervention of Turkey or Russia, or both of them.”
Armenia, which has a Christian-majority population, and Azerbaijan – which is mainly Muslim – first clashed in the 1980s over Nagorno-Karabakh.
The breakaway region is inside Azerbaijan but is mostly populated and run by ethnic Armenians.
The latest fighting has revived concern over stability in the South Caucasus, a corridor for pipelines carrying oil and gas to world markets.
Authorities in Nagorno-Karabakh said that 27 of its soldiers had been killed in fighting with Azeri forces on Monday, after saying that 31 soldiers had died on Sunday and more 100 wounded.
The general prosecutor’s office in Azerbaijan said two Azeri civilians were killed on Monday, after five were killed on Sunday, and 30 civilians had been wounded.
There was no official information about Azeri military casualties.
It was not immediately clear what sparked the fighting, the heaviest since clashes in July killed 16 people from both sides.
The European Union urged both sides to halt the fighting and return to the negotiating table, following similar calls by Iran, Russia, France and the United States.
European Commission spokesman Peter Stano said: “We hope and we urge everyone to everything they can in order to prevent an all-out war from breaking out, because this is the last thing the region needs.
“There is no military solution to this conflict.”
Under international law, Nagorno-Karabakh is recognised as part of Azerbaijan. But the ethnic Armenians who make up the vast majority of the population reject Azeri rule.
They have run their own affairs, with support from Armenia, since Nagorno-Karabakh broke away from Azerbaijan in a conflict that erupted as the Soviet Union collapsed in 1991.
Although a ceasefire was agreed in 1994, Azerbaijan and Armenia frequently accuse each other of attacks around Nagorno-Karabakh and along the separate Azeri-Armenian frontier.