Clashes raged between Armenian and Azerbaijani forces on Friday despite calls for a ceasefire, as French President Emmanuel Macron warned Turkey against the alleged deployment of extremists to the war zone.
Macron said intelligence reports had established that 300 fighters from "extremist groups" in Syria had passed through Turkey en route to Azerbaijan, saying that "a red line has been crossed" and demanding an explanation.
Ankara is backing its longtime ally Baku in the fighting over Nagorny Karabakh, an ethnic Armenian province that broke away from Azerbaijan in a bitterly fought war in the 1990s.
Armenia and Azerbaijan have been locked in a simmering conflict for decades over the region and new fighting that erupted on Sunday has been the heaviest in decades.
Nearly 200 people have been confirmed killed, including more than 30 civilians, and there are fears of the fighting expanding into an all-out, multi-front war that could suck in regional powers Turkey and Russia.
As the clashes entered a sixth day on Friday, the defense ministry of Karabakh's separatist government reported the deaths of 54 more of its troops.
It said there was fighting all along the frontline after "a relatively calmer night".
Azerbaijan's defense ministry also said the fighting was ongoing, and both sides claimed to have inflicted heavy losses.
Armenian Prime Minister Nikol Pashinyan and Azerbaijani leader Ilham Aliyev have rejected calls for talks.
Russia, US, France appeal for talks
Russia and Western countries have pressed for an immediate ceasefire and negotiations, while Turkey has been fierce in its support for Baku, accusing Armenia of occupying Azerbaijani lands.
Macron issued his warning to Ankara at an EU summit in Brussels on Thursday, urging "all NATO partners to face up to the behavior of a NATO member".
In a joint appeal on Thursday, Russian President Vladimir Putin, US President Donald Trump and Macron urged the two sides to return to negotiations aimed at resolving their longstanding territorial dispute.
Russia also suggested it was making progress in diplomatic efforts with Turkey.
It said Foreign Minister Sergei Lavrov and Turkish counterpart Mevlut Cavusoglu had confirmed they were ready for "close coordination" to stabilize the situation.
Yerevan is in a military alliance of ex-Soviet countries led by Moscow and has accused Turkey of directly supporting Azerbaijan in the fighting, by deploying aircraft in support of Baku and sending mercenaries from northern Syria to join the fighting.
Armenia has recorded the deaths of 158 soldiers and 13 civilians since Sunday. Azerbaijan has not reported any military casualties but said 19 civilians were killed after Armenian shelling.
Karabakh's declaration of independence from Azerbaijan sparked a war in the early 1990s that claimed 30,000 lives, but it is still not recognized as independent by any country, including Armenia.
Armenia and Karabakh declared martial law and military mobilization Sunday, while Azerbaijan imposed military rule and a curfew in large cities.
Talks to resolve the conflict have largely stalled since a 1994 ceasefire agreement.
