Russian investigators have opened a criminal case on the shooting down of a Russian military helicopter by Azerbaijani forces—and over the Armenia-Azerbaijan border.

A criminal case has been filed under the article on the violation of flights or of the rules for their preparation, Interfax reported, citing an informed source.

According to the agency's interlocutor, the aforesaid article may be changed for a more severe criminal case.

The investigation is being conducted by the investigators of the 102nd Russian Military Base in Gyumri, Armenia.

A Russian military helicopter, which was accompanying a convoy of the aforesaid military base, was shot down Monday on the Armenian-Azerbaijani border. Two people were killed and one was injured. The helicopter was shot down more than 100 km away from the Nagorno-Karabakh (Artsakh) conflict zone.

Azerbaijan claimed responsibility for the incident, saying it had "mistakenly" shot down the helicopter, apologized and promised to pay compensation.