Belarus opposition leaders Sviatlana Tsikhanouskaya, Olga Kovalkova, Maxim Znak, Maria Kolesnikova, Sergei Dylevsky and others are being investigated in relation to forming an "extremist association," Belarus' Public Prosecutor's Office said on Monday.
The office accused the group of forming a "conspiracy" with the objective of seizing control via a coup, the news agency DPA reported.
The criminal proceedings are widely considered as politically motivated as strongman Alexander Lukashenko seeks to silence his opponents.
Government critic Kolesnikova has been in custody since September. The 38-year-old has said security officers put a bag over her head during her arrest and told her she would be taken out of the country "alive or in bits."
Tsikhanouskaya seeks support
The group of opposition activists announced the creation of the Coordination Council in the wake of the country's August 9 presidential election, which was widely considered fraudulent.
The election commission gave the incumbent seeking a sixth term 80% of the vote compared to 10% for his nearest rival, Tsikhanouskaya.
Lukashenko condemned the Coordination Council as extremist and rejected both overtures for dialogue and calls for his resignation.
The anti-government movement has initiated protests since the presidential election, with hundreds of thousands of people taking part.
Most of the members of the council have since left the country under pressure from the authorities.
From her exile in neighboring Lithuania, Tikhanovskaya has orchestrated protests, met regularly with heads of state and government to drum up support, and is currently in the process of forming a government in exile.