Baku, Azerbaijan – UN Security Council expressed concern about the clashes, after Secretary-General Antonio Guterres called for a halt to fighting.

Nagorno-Karabakh is a breakaway region inside Azerbaijan but run by ethnic Armenians and backed by Armenia.

Armenia and Azerbaijan accused one another of firing directly into each other’s territory and rejected pressure to hold peace talks as their conflict over the enclave of Nagorno-Karabakh threatened to descend into all-out war.

Both countries reported on Tuesday firing from the other side across their shared border, well to the west of the breakaway Nagorno-Karabakh region over which fierce fighting broke out between Azeri and ethnic Armenian forces on Sunday.

The incidents signalled a further escalation of the conflict despite urgent appeals from Russia, the United States and others to halt the fighting.

The conflict has reignited concerns about stability in the South Caucasus region, and threatens to drag in Turkey and Russia.

Azeri President Ilham Aliyev, speaking to Russian state television, flatly ruled out any possibility of talks. Armenian Prime Minister Nikol Pashinyan told the same channel there could be no negotiations while fighting continued.

Nagorno-Karabakh is a breakaway region inside Azerbaijan that is controlled by ethnic Armenians and backed by Armenia. It broke away from Azerbaijan in a war during the 1990s but is not recognised by any country as an independent republic.

Dozens of people have been reported killed and hundreds wounded since clashes between Azerbaijan and ethnic Armenian forces broke out on Sunday.

After a closed-door discussion on Tuesday the 15-member United Nations Security Council “expressed concern” about the clashes, condemned the use of force and backed a call by UN Secretary-General Antonio Guterres for an immediate halt to fighting.

Further stoking tensions between the two former Soviet republics, Armenia said a Turkish F-16 fighter jet had shot down one of its warplanes over Armenian airspace, killing the pilot.

It provided no evidence of the incident. Turkey has denied the claim.

“Armenia should withdraw from the territories under its occupation instead of resorting to cheap propaganda tricks,” Turkey said.

Russia said President Vladimir Putin spoke by phone to Pashinyan for the second time since the start of the crisis and said all sides should take measures to de-escalate. It has not made public any contacts between Putin and Aliyev.

Russia was in constant contact with Turkey, Armenia and Azerbaijan, and any talk of providing military support for the opposing sides would only add fuel to the fire, it said.

Azerbaijan’s prosecutor’s office said 12 Azeri civilians had so far been killed and 35 wounded by Armenian fire. The Azeri side has not disclosed military casualties.

Nagorno-Karabakh has reported the loss of at least 84 soldiers.

Azerbaijan’s defence ministry said that from Vardenis the Armenian army had shelled the Dashkesan region inside Azerbaijan.

In Nagorno-Karabakh, signs of escalating and widening conflict.

Armenia accuses Azerbaijan of using long-range weaponry in the disputed enclave and threatens to reciprocate, raising concerns that
fighting could spread to the territories of both countries.

Armenia said Tuesday that Azerbaijan was employing longer range and more destructive types of artillery in fighting over the Nagorno-Karabakh region, now in its third day, and threatened to deploy heavier weapons of its own.

The Armenian Ministry of Defense also said that one of its jets had been shot down by a Turkish F-16. A spokeswoman said the Turkish plane had taken off in Azerbaijan, flown into Armenia, and shot down the Armenian military airplane.

Azerbaijan and Turkey denied this had happened. It was not immediately possible to confirm the Armenian claims about the planes or the Azerbaijani artillery barrage.

Fighting in Nagorno-Karabakh, an Armenian separatist enclave in Azerbaijan in a remote mountain area north of Turkey and Iran, began on Sunday and has killed at least dozens of people, threatening to pull in two major powers in the region, Russia and Turkey.

The conflict began after diplomats missed chances to tamp down simmering tensions in the region over the summer, in part because
their governments were distracted by the pandemic, analysts have said.

The Armenian Defense Ministry said that Azerbaijan had begun firing from two powerful Soviet-made rocket artillery systems. In response, the Armenian military threatened it would roll out unspecified heavier weapons.

Also on Tuesday, the Armenian Foreign Ministry said a civilian had been killed inside Armenia in a strike by a Turkish-made armed drone. Armenia has a mutual defense treaty with Russia but has not asked that it be activated because of the fighting.

Armenia and Azerbaijan fought a war over Nagorno-Karabakh in the early 1990s, a conflict that ended in a stalemate with a cease-fire but no settlement.

Periodic border skirmishes have ensued since then. But the fighting now is distinct from clashes in recent years because of its scale and because Turkey is more openly backing Azerbaijan, a fellow Turkic-speaking country.

Turkish armed drones, similar to the United States’ Predator, are being used widely for the first time in the occupied region in the fighting that broke out this weekend.

Their appearance was another indication that the Nagorno-Karabakh conflict, which simmered for decades without much interest from outside powers, has now become part of Russia’s broader competition for influence with Turkey.

The fighting has so far taken place in mostly unpopulated areas formerly inhabited by ethnic Azerbaijanis in a security buffer zone around the Nagorno-Karabakh region, which has declared itself an independent country but is not recognized as such by other nations. About 600,000 Azerbaijanis were driven from Nagorno-Karabakh in the war three decades ago.

But shelling has also hit populated areas in Nagorno-Karabakh. The military of the breakaway enclave said Tuesday that 84 of its soldiers had died in the fighting.

Both Armenia and Azerbaijan have in the past threatened to target strategic infrastructure in one another’s countries, such as dams or power plants, if war came. The Russian-made Tornado, or Smerch, rocket launcher that Armenia on Tuesday accused Azerbaijan of deploying, for example, has a range of more than 50 miles, enough to reach well into Armenia.

On Tuesday, the Turkish foreign ministry said that Turkey would support Azerbaijan diplomatically and “on the battlefield” if needed. Russia and two other states mediating the 1990s truce, the United States and France, have called for another negotiated cease-fire.