Armenian Prime Minister Nikol Pashinyan has warned of an "attempted military coup", after the country's armed forces said he and his cabinet must resign.
He urged his supporters to take to the streets in the capital Yerevan.
The army earlier said the prime minister was "no longer able to make reasonable decisions" after he sacked a top military commander.
Mr Pashinyan has faced mass protests after losing last year's conflict with Azerbaijan over Nagorno-Karabakh.
Nagorno-Karabakh is an enclave internationally recognised as part of Azerbaijan but which had been controlled by ethnic Armenians since a 1994 truce.
During the bloody six-weeks of fighting late last year, Azerbaijan not only recaptured areas around the enclave but also took the key town of Shusha inside it.