(Baku Daily) - President Ilham Aliyev praised his army for the November 12 downing of an Armenian helicopter that killed three crew members in the worst military incident between the two countries in 20 years.

Aliyev promised more armed responses to Armenian provocations in future during an “operational meeting” on November 15 with his generals in the western Shamkir District, his office said.

Azerbaijan used a Russian-made portable anti-aircraft missile to shoot down the Mi-24 military helicopter that tried to attack Azeri positions in the Agdam District, east of the Armenian-occupied Nagorno-Karabakh region, the Defense Ministry in Baku said on its website.

Armenia claimed that the helicopter was on a training flight and was unarmed when it was hit. 

Armenians captured Nagorno-Karabakh and seven adjacent districts from Azerbaijan in a war after the breakup of the Soviet Union in 1991. 

Last week’s incident tests a cease-fire that’s held since Russia brokered a deal in 1994. It marks the first time an aircraft has been shot down in the conflict zone since hostilities halted, according to the Organization for Security and Cooperation in Europe’s Minsk Group, which mediates peace talks between the two countries. Armenia and Russia have a mutual-defense pact.

Companies led by BP Plc (BP/), which have together invested more than $50 billion in Azerbaijan’s energy projects in the past 20 years, signed $45 billion of agreements in December to pipe Azeri natural gas to Europe from 2019.