Myanmar's National Unity Government, formed by pro-democracy forces, has called for a revolt against military rule in the Southeast Asian nation.
The shadow government is made up of ousted lawmakers supporting Aung San Suu Kyi, along with representatives of ethnic minorities.
Duwa Lashi La, the NUG's acting president, posted a speech online on Tuesday declaring the launch of a "defensive war" against the military junta.
The acting president noted that the military continues to carry out killings, torture and detention.
He called on the people's defense force, formed by armed citizens across the country, and multiple ethnic minority militants to attack the military and its facilities.
Duwa Lashi La also asked other civilians to support the defense force's activities while remaining vigilant.
Citizens and ethnic minority groups in many parts of the country continue to offer resistance to the military, which seized power in a February 1 coup.
It is believed the speech is aimed at making the presence of pro-democracy forces known ahead of the United Nations General Assembly due to start later this month.
The military may respond to the speech with further crackdowns.