A man from Mabanda, Burundi, casts his ballot in the national referendum on the draft of post-transition constitution (file photo). (Photo Courtesy UN Photo/Martine Perret)

Burundi's main opposition bloc, the Democratic Alliance for Change, has announced it will form an extra-parliamentary opposition for the next five years.

The announcement follows the group's decision last month to boycott the whole electoral process in Burundi in protest at poll rigging.

However, the group faces many challenges. Aside from the government crackdown on the opposition, one political party decided to pull out of the alliance.

Speaking in a news conference on Tuesday, the head of the bloc Leonce Ngendakumana said as a responsible opposition, out of the institutions, the group will be in a better position to denounce violations of human rights, corruption and mismanagement of public funds.

The group pledged to work in close collaboration with the civil society organisations and media.

But the task will not be easy.

Since June, the government crackdown on the opposition has pushed three main opposition leaders to go into hiding.

Ex-rebel chief Agathon Rwasa, former journalist Alexis Sinduhije, and the head of another opposition bloc Leonard Nyangoma left the country for fear of arrest.

Burundi's government has even endorsed the ousting of the National Liberation Forces (FNL) leader Agathon Rwasa, who was deposed by dissident party members.

The group had pulled out of the electoral process over rigging in communal elections and renounced its seats.