NATO called on Armenia and Azerbaijan to cease hostilities and pledged support for the normalization of relations after fighting flared up in Karabakh earlier this week.
"NATO calls for an immediate end of hostilities between Azerbaijani and Armenian forces," Javier Colomina, the NATO secretary-general's special representative for the Caucasus and Central Asia, said on Twitter.
He added that the alliance urges both sides to "de-escalate and return to the negotiating table."
"NATO supports the normalization of relations between Armenia and Azerbaijan," Colomina added.
The European Union, including the office of European Council President Charles Michel and Toivo Klaar, the bloc's special representative for the South Caucasus, has also been "in intense contact with both sides over the past days," Anadolu Agency (AA) learned from an EU official.
Michel has already spoken with Armenian Prime Minister Nikol Pashinian and will soon talk to Azerbaijan's President Ilham Aliyev, the source said.
The EU pushes for an "immediate de-escalation" and dialogue on other aspects of the relations, the official added.
Azerbaijan said it launched a retaliatory operation on Wednesday against Armenian forces in the Karabakh region, previously referred to as Nagorno-Karabakh, after Armenia opened fire and killed an Azerbaijani soldier, according to its Defense Ministry.
Relations between the former Soviet republics have been tense since 1991 when the Armenian military occupied Nagorno-Karabakh, a territory internationally recognized as part of Azerbaijan, and seven adjacent regions.
After new clashes during the fall of 2020, Azerbaijan liberated several cities and over 300 settlements and villages occupied by Armenia for almost 30 years.
The fighting ended in November 2020 with a Russia-brokered deal.
In a statement, Azerbaijan's Foreign Ministry said it has repeatedly pointed out Armenia's failure to fulfill the provisions of the agreement, particularly how the Armenian armed forces have not yet pulled out of Azerbaijani territories.