Various countries, including Russia, Germany, France and the U.S. appealed for calm in Karabakh, amid Azerbaijan's ongoing counterterrorism operation in the region.
Azerbaijan on Tuesday said that it had launched "counterterrorism measures" in the Karabakh region to uphold provisions outlined in the November 2020 trilateral peace agreement it signed with Russia and Armenia.
Steps were taken to "suppress large-scale provocations in the Karabakh economic region, to disarm and secure the withdrawal of formations of Armenia's armed forces from our territories, neutralize their military infrastructure, provide the safety of the civilian population which returned to territories liberated from occupation, civilians involved in construction and restoration work and our military personnel, and ultimately restore the constitutional order of the Republic of Azerbaijan," the Azerbaijani Defense Ministry said in a statement.
Positions on the front line, firing points of the formations of Armenia's armed forces, as well as combat assets and military facilities are being "incapacitated" using "high-precision weapons," the ministry added.
French President Emmanuel Macron told Armenian Prime Minister Nikol Pashinian in a phone call he would call for an emergency meeting of the U.N. Security Council because of the situation in Karabakh, the Armenian government said Tuesday.
The United States is engaging in diplomatic outreach after Azerbaijan launched its operation in the Karabakh region, U.S. officials said, adding that the incident was particularly dangerous.
A senior U.S. State Department official said U.S. Secretary of State Antony Blinken was likely to get involved in the next 24 hours in the diplomatic engagement already underway on the tensions between Armenia and Azerbaijan.
Armenia's Prime Minister Pashinian and Blinken discussed the situation and stated the need for de-escalation, Interfax reported, citing the Armenian government.
A second senior State Department official said the incident overnight was "particularly egregious and particularly dangerous, so we'll obviously be in touch with all sides."
This week, the International Committee of the Red Cross (ICRC) was able to make simultaneous aid deliveries via the Lachin corridor and a separate road linking Karabakh to the Azerbaijani city of Aghdam.
"It's concerning that this happened overnight, especially because we did see some progress yesterday with shipments moving through the Lachin corridor," the first official said.
Analysts say successive rounds of talks, mediated variously by the European Union, the United States and Russia, have brought the two sides closer to a permanent peace treaty than they have been for years, but a final settlement remains elusive.
German Foreign Minister Annalena Baerbock has demanded that Azerbaijan immediately end its operation in Karabakh.
A lasting peace between Azerbaijan and Armenia can only be achieved at the negotiating table, she said, adding that Berlin supports talks led by the European Union.
"In view of today's escalation, these are more urgent than ever before."
The Kremlin on Tuesday also called for calm in the Karabakh region.
"We are concerned about the sharp escalation of tension and the beginning of hostilities," Kremlin spokesperson Dmitry Peskov told reporters.
"The first thing for us, against the background of the military operation carried out by the Azerbaijani Armed Forces, is to ensure the safety of the civilian population of Karabakh."
Peskov said the Russian military had been in contact with both Baku and Yerevan and that Moscow was urging talks.
"Our military is working to return the settlement process to the political and diplomatic path," Peskov said, adding that the basis for talks was the ceasefire agreement brokered by Russia that ended a 2020 war in which Azerbaijan made significant gains.
"We urge everyone to follow the provisions of these documents, naturally, taking into account those new realities, meaning the fact that the Armenian side recognized the territory of Azerbaijan as of 1991."
Karabakh is a longstanding source of strain between the South Caucasus neighbors, which fought two wars over the territory – first in the early 1990s and again in 2020 when Azerbaijan liberated several cities, villages and settlements from illegal Armenian occupation during 44 days of clashes. Fears of a fresh war have been building in recent months, with Armenia accusing Azerbaijan of a troop buildup and decrying a blockade of the Lachin corridor. "Localized anti-terrorist measures have been launched in the region," Azerbaijan’s Defense Ministry said, accusing Armenian-backed forces of repeated shelling and incursions.