Dozens of people have been killed in a second day of fighting between azeri and armenian troops in nagorno-karabakh, the most serious clashes over the disputed enclave for four years.

Authorities in nagorno-karabakh, which is within azerbaijans borders but populated by ethnic armenians, said that 28 service personnel had died in fighting on monday, taking the total dead since the latest fighting erupted to 59. azerbaijan did not disclose military casualties but said six civilians had been killed by armenian artillery fire.

The clashes in the caucasus mountains, which began on sunday with an azerbaijani aerial and missile attack on nagorno-karabakh which it described as a counteroffensive against armenia are the worst since 2016, when hundreds died in a five-day war.

Azerbaijan said on monday that it had seized strategic heights around the key village of talish and would use territorial gains to press its neighbour for concessions at future peace negotiations. a turkish security source said azerbaijan had hit 400 targets and destroyed more than 10 armenian military air defence systems and close to 20 armoured vehicles, including tanks.

The escalation threatens to spill over into an all-out war involving turkey, which backs mostly turkic azerbaijan, and russia, which has a defence agreement with overwhelmingly christian armenia. the us, eu, and russia have all called for an immediate ceasefire. it also threatens the stability of a european energy supply corridor via a pipeline that runs through turkey.

Moscow and ankara already back opposing sides in the libyan and syrian civil wars. armen sarkissian, armenias president, claimed that turkey had provided drones, mercenaries and f-16 fighter jets to support azerbaijan in the conflict.

Recep tayyip erdogan, turkeys president, called for armenia to immediately withdraw from what he said were occupied azerbaijani lands.

It is time to put an end to this crisis, which began with the occupation of nagorno-karabakh, he said in a speech on monday. the region will once again be able to embrace peace and tranquility if armenia immediately withdraws from the azeri lands that it is occupying.

Armenias ambassador to moscow accused turkey of sending 4,000 mercenaries from syria to fight alongside azerbaijans armed forces. azerbaijan denied the claims while saying it had killed a large number of ethnicarmenianmercenaries from syria and various other countries.

Youssef hammoud, spokesperson for the turkish-backed syrian national army rebels in north-west syria, denied the group had sent mercenaries. omer celik, a spokesman for turkeys ruling party, described the claims that turkey had dispatched syrian mercenaries to the region as lies and a provocation against turkey.

Russia, which leads mediation efforts alongside the us and france, said it would use its influence and historically good relations with the former soviet nations to seek a ceasefire. its important now to stop the fighting rather than try to find out whos right and whos wrong, dmitry peskov, the kremlins spokesman, told reporters.nagorno-karabakh, an enclave of fewer than 150,000 people, broke away from azerbaijan in the dying days of the soviet union and runs its affairs with political and military support from armenia.

A war began in the early 1990s and claimed thousands of lives before a ceasefire was signed in 1994. armenia and azerbaijan have yet to strike a full peace deal and regularly clash along the line of contact, most recently in july, when at least 20 people died in fighting about 300km north of the enclave.

Tensions rose last week when ilham aliyev, azerbaijans president, claimed that armenian forces were massing in preparation for war. armenia accused mr aliyev of fabricating the claim as a pretext to start its military operations.

Additional reporting by asmaa al-omar in istanbul