Whenever fighting has erupted between armenia and azerbaijan over the disputed territories claimed by both neighbours, demands from moscow have ultimately forced the two post-soviet states to the negotiating table.

This time, however, russias calls to stop the escalating violence in nagorno-karabakh that began on sunday have so far fallen on deaf ears, thanks in part to the rise of turkey as a regional power that has altered the delicate balance in the sensitive caucasus mountains region.

Ankaras support for its neighbour azerbaijan and sabre-rattling rhetoric has fanned the most violent flare-up for several years in a decades-long conflict, and created a significant headache for russian president vladimir putin by challenging moscows regional hegemony.

While russia has traditionally sought to remain neutral in the territorial dispute moscow considers both former soviet states as allies it has a military base in armenia and a defence pact with the country that contains a mutual assistance clause in case of attack from external countries.

At the same time, turkeys full-blooded support for azerbaijan in the conflict has emboldened baku, analysts say, and chipped away at moscows influence over the azeri leadership.

That has added another flashpoint to moscow and ankaras list of conflicts where the two regional powers and their strongman leaders who have sought to strike an uneasy alliance over trade, energy and mutual distrust of the west find themselves at odds, alongside syria and libya.

Turkeys growing involvement in the south caucasus through azerbaijan is a fact which russia does not relish. russian and turkish interests clash here more than anywhere, said dmitri trenin, head of the carnegie moscow center think-tank, adding: putin and erdogan have never been true allies, and never will.

He added: what they manage to do instead is to capitalise on their parallel interests and to play down differences and divisions, so that these do not lead to direct conflict between russia and turkey.

Recep tayyip erdogan, turkeys president, has adopted an increasingly assertive foreign policy in recent years, using overseas military deployments and bombastic rhetoric to stoke nationalist sentiment at home.

Mr erdogans combative response to the clashes, which saw him attack the armenian leadership and offer full support to azerbaijan, marks a break with previous rounds of fighting in the region.

This signals quite a big shift in turkish policy, said thomas de waal, an expert on the region and author of black garden: armenia and azerbaijan through peace and war. turkey has always offered political support to azerbaijan but has also said the conflict must be resolved peacefully... theres been a geopolitical equilibrium where no side has really backed one side over the other... now suddenly one of the major regional actors is backing azerbaijan.

Turkey views azerbaijan as a brother country with shared cultural, linguistic and ethnic roots. the two have close trade ties, especially in the field of energy.

Armenias foreign ministry on monday accused turkey of a direct presence on the ground in the conflict, including weapons and fighter planes. turkish media had trumpeted the use of what they said were drones made by a defence company run by one of mr erdogans sons-in-law and his family.

Map showing oil and gas pipelines through azerbaijan

But a turkish official dismissed armenian claims that turkish military experts and turkish-backed syrian mercenaries were taking part in the conflict as baseless accusations.

As the fighting escalated on monday, azerbaijans defence ministry released a video it said depicted missile attacks on two armenian tanks. it claimed its armed forces had destroyed 26 armenian tanks since the hostilities began on sunday. six azeri citizens had been killed by armenian artillery, baku said.

Nato and the eu have called on the warring sides to reach a ceasefire. azerbaijan hosts a gas pipeline that carries gas to turkey and onwards to europe, a route viewed by brussels as a critical alternative to gas supplies from russia.

Russias desire to please both sides and turkeys position in the conflict means moscow will probably rely on diplomacy rather than an aggressive military response, in contrast to its response to other territorial conflicts in the post-soviet region, such as in ukraine and georgia.

The kremlin has sought to play down any suggestions it could join the fighting. russias defence pact with armenia does not cover nagorno-karabakh, meaning yerevan could only request moscow to deploy troops if there was an attack on undisputed armenian territory.

Theres little expectation of the reliance or durability of the so-called security pact with russia, said richard giragosian, director of the yerevan-based regional studies center think-tank. we will probably see an uncharacteristically delicate foreign policy response from moscow, he added.

Speaking on monday, kremlins spokesman dmitry peskov said it was important now to stop the fighting rather than try to find out who is right and who is wrong.

Russia has always assumed a balanced position...and has good relations with both armenia and azerbaijan, mr peskov said, adding moscow was also in full contact with ankara over the dispute.

Sinan ulgen, a former turkish diplomat who now chairs the istanbul-based think-tank edam, said turkey and russia would strive to find a way through the conflict without harming their bilateral relationship.

But he also warned of the risks if the fighting spread into places such as the autonomous exclave of nakhchivan, which borders armenia and which ankara has a 1921 treaty obligation to defend.

If we see this conflict spill over into other parts of the geography, in particular nakhchivan, that will trigger a much more difficult episode between turkey and russia which will come on top of the existing theatres of conflict in syria and libya.