The leaders of russia, france and the us have issued a joint demand for an immediate ceasefire between armenian and azerbaijani forces, as the death toll from a spiralling conflict between the neighbours over a territorial dispute continued to rise.

Dozens of people have been killed and hundreds more injured after a decades-old struggle for control of nagorno-karabakh, an armenia-controlled region inside azerbaijan, erupted this weekend in the worst military clashes for decades.

We condemn in the strongest terms the recent escalation of violence...[and] call for an immediate cessation of hostilities between the relevant military forces, presidents vladimir putin of russia, emmanuel macron of france and donald trump of the us said in a joint statement.

The demand by the co-chairs of the minsk group, the body that has overseen negotiations in the dispute since it was set up in 1992, ratcheted up pressure on turkey. president recep tayyip erdogans military support for azerbaijan and warmongering rhetoric has drawn condemnation from both moscow and ankaras nato allies.

Mr erdogan, who has broken with ankaras previous tradition of urging de-escalation in the long-running conflict, rejected the ceasefire demand.

It is not acceptable that the minsk group is still in search of a ceasefire, he said in a speech. in order for there to be a solution, the occupiers must withdraw from these lands. its time for results, and our azeri brothers and sisters have taken matters into their own hands.

The conflict has raised tensions between moscow and ankara, which already back opposing militaries in the civil wars in libya and syria. russia has a military base in armenia and a mutual defence pact with the country, though that does not cover the disputed territory.

Russia resents efforts by mr erdogan to expand turkeys influence in the historically moscow-dominated caucasus region through its warm ties with azerbaijan.

Both moscow and paris have accused mr erdogan of sending mercenary fighters from syria to azerbaijan. baku has denied that any irregular forces are assisting their troops.

Mr macron said france had evidence that syrian jihadis had travelled from the turkish city of gaziantep, close to the syrian border, to fight in nagorno-karabakh.

This is a very serious new fact, which changes the situation, he told reporters on the sidelines of an eu summit in brussels, where bloc leaders are due to discuss both nagorno-karabakh and turkey.

Mr macron has taken an increasingly tough line against nato ally turkey in recent months, over subjects ranging from the civil war in libya to ankaras contentious gas exploration in the eastern mediterranean sea.

Mr erdogan on thursday reiterated a promise that turkey would continue to support azerbaijan in every way that we can.

The path to peace in this region is the withdrawal of armenian occupation from every inch of azerbaijans soil, he said. i am warning those who support this rogue state that they will be held to account by the shared conscience of humanity.

The international ceasefire demand came after the kremlin warned turkey that transporting the militants from syria risked extreme danger and that military support by third countries was a provocation for further escalation of tensions.

The statement from the co-chairs of the minsk group also called on baku and yerevan to immediately undertake commitments in good faith and without setting preconditions to resume negotiations towards a peace settlement.

Mountainous nagorno-karabakh was an autonomous region when both armenia and azerbaijan were part of the soviet union. the conflict began when the regions armenian-majority population sought to join armenia, sparking a war that killed more than 20,000 people before a russia-brokered ceasefire in 1994 ushered in an uneasy stalemate.