azerbaijain tanks
© Azerbaijani Defence Ministry (AFP)
Armenia on September 29 said a Turkish F-16 shot down one of its warplanes, a claim immediately denied by Ankara as "absolutely untrue."

Yerevan's claim came as fighting between Armenia and Azerbaijan over the disputed region of Nagorno-Karabakh continued for a third day in a major flare-up of the decades-old conflict over the territory amid international calls for an end to the deadly hostilities.

The UN Security Council is expected to hold emergency talks later on September 29 to discuss the fighting, which has threatened to draw in regional powers Russia and Turkey, which is a close ally of Azerbaijan.

An Armenian Defense Ministry spokeswoman wrote on Facebook that the Sukhoi Su-25 warplane had been on a military assignment in Armenian airspace when it was downed by an F-16 fighter jet owned by the Turkish air force.

Shushan Stepanyan added that the "Armenian pilot has heroically died."

Fahrettin Altun, a spokesman for Turkey's presidency, denied the accusation, saying, "The claim that Turkey shot down an Armenian fighter jet is absolutely untrue."

"Armenia should withdraw from the territories under its occupation instead of resorting to cheap propaganda tricks," Altun said.

Altun said Turkey "will be fully committed to helping Azerbaijan take back its occupied lands and to defending their rights and interests under international law."

"We hope that today's UN Security Council meeting will establish a strong foundation for a solution," he tweeted.

Azerbaijan's Defense Ministry also denied that a Turkish fighter jet had shot down an Armenian plane.

Earlier on September 29, dozens of deaths were reported in the latest escalation between forces of the two Caucasus nations with the Azerbaijani Defense Ministry saying that the Armenian military shelled the Dashkesan region of Azerbaijan -- an accusation rejected by Yerevan as "absolutely false."

The clashes over Nagorno-Karabakh are the heaviest seen since 2016 and have reignited concern over stability in the South Caucasus region, a corridor for pipelines carrying oil and gas to world markets.

"On the night of September 28-29, intense battles continued along the entire front line," Azerbaijan's Defense Ministry said in a statement, referring to the so-called Line of Contact that separates Armenian and Azerbaijani forces.

The Armenian Defense Ministry added that "battles with varying intensity continue."

During a visit to Greece on September 29, U.S. Secretary of State Mike Pompeo said that both sides "must stop the violence" and work with the Minsk group of the Organization for Security and Cooperation in Europe (OSCE) to "return to substantive negotiations as quickly as possible."

German Chancellor Angela Merkel "urgently called for an immediate cease-fire and a return to the negotiating table" in phone calls with the leaders of Armenia and Azerbaijan, according to her spokesman.

Steffen Seibert said Merkel spoke with Azerbaijani President Ilham Aliyev on September 29 and Armenian Prime Minister Nikol Pashinian the day before.

That came on the heels of a joint statement by the foreign ministers of Britain and Canada, who expressed concern over the "large-scale military action" in Nagorno-Karabakh.

"Reports of shelling of settlements and civilian casualties are deeply concerning. We call for the immediate end of hostilities, respect for the cease-fire agreement, and the protection of civilians," British Foreign Secretary Dominic Raab and Canadian Foreign Minister Francois-Philippe Champagne said.

Raab and Champagne also backed negotiations through the Minsk process of the OSCE.

UN Secretary-General Antonio Guterres has called directly on the leaders of Armenia and Azerbaijan to immediately halt hostilities.

Guterres is also pushing the two sides to resume talks and accept the redeployment of monitors from the OSCE to the region.

The European Court of Human Rights said on September 28 that the Armenian government had asked it to issue urgent instructions to Azerbaijan to stop attacks on civilians as well as military advances toward civilian settlements in Armenia and Nagorno-Karabakh.

The long-simmering conflict in the volatile South Caucasus erupted on September 27 into the deadliest bouts of fighting in four years in the ethnic Armenian separatist enclave inside Azerbaijan.

Late on September 28, the separatists in Nagorno-Karabakh reported that another 26 Armenian servicemen had been killed in the latest fighting, bringing its total losses to 84.

Azerbaijan said at least 10 civilians had been killed and some 30 wounded.

Armenian reports that they have killed Azerbaijani forces have not been confirmed by Baku.

Nagorno-Karabakh has long experienced periodic border skirmishes along the front line of Europe's longest-running conflict.

Armenia declared martial law and a total mobilization on September 27 in response to what it said was Azerbaijani attacks on the enclave, including in the regional capital of Stepanakert.

Azerbaijan responded by declaring a partial military mobilization on September 28.

Both sides have fielded helicopters, drones, tanks, and artillery during the first two days of fighting.

Yerevan has accused Ankara of having a "direct presence on the ground" and supplying its ally Baku with weapons, including drones -- a claim denied by Azerbaijan.

Turkish President Recep Tayyip Erdogan on September 28 called on Armenia to immediately end its "occupation" of the region and withdraw, saying this was the only way to secure peace.

Earlier on September 29, Kremlin spokesman Dmitry Peskov called on "all sides, especially partner countries such as Turkey, to do all they can for a cease-fire and get back to a peaceful settlement of this conflict using political and diplomatic means."

"Any statements about some kind of support and military activity undoubtedly add fuel to the flames," Peskov told reporters.

Moscow sells weapons to both Azerbaijan and Armenia, but has a military base in Armenia and favors that strategic partnership.

The Nagorno-Karabakh conflict emerged during the breakup of the Soviet Union, when the region and seven adjacent districts of Azerbaijan were seized by Armenian-backed separatists who declared independence amid a 1988-94 conflict that killed at least 30,000 people and displaced hundreds of thousands.

Since a fragile, Russian-brokered truce in 1994, the region has been under the control of ethnic Armenian forces that Azerbaijan says include troops supplied by Armenia.

The region's claim to independence has not been recognized by any country.