One of those arrested said in footage released by the secret service that he had allegedly spied for Azerbaijan, with whom Armenia's long-simmering conflict over Nagorno-Karabakh flared anew into war late last year.

The military intelligence department of Armenia's national security service said it had "arrested 19 people suspected of high treason, some of whom confessed."

It said that "a foreign secret service has set up a network that involved Armenian nationals, employees of the country's armed forces."

It added: "They had access to classified documents and were collecting information about Armenian military facilities, weapons, and personnel."

The statement gave no further detail.

In autumn 2020, the protracted territorial dispute over Azerbaijan's Armenian-populated Nagorno-Karabakh region flared into an all-out war that claimed more than 6,500 lives.

The 44-day war ended with a Russian-brokered ceasefire agreement under which Armenia ceded swathes of territory it had controlled for decades.

Armenian Prime Minister Nikol Pashinyan and Azerbaijani President Ilham Aliyev met in December twice, in Moscow and Brussels, for rare face-to-face talks to discuss normalisation.

Ethnic Armenian separatists in Nagorno-Karabakh broke away from Azerbaijan as the Soviet Union collapsed in 1991, and an ensuing armed conflict claimed around 30,000 lives.