The leader of a Guinea Bissau civil society group critical of President Jose Mario Vaz, was violently attacked in his own home Friday by unidentified assailants, his group told AFP.

Legio Monteiro is head of the Vigilant Non-Compliant Citizen's Movement, which is considered close to the ruling PAIGC party and which is campaigning to end a long-running political crisis between the party and the president.

Monteiro was struck on the head and body and his injuries are being treated at a secret location, sources close to him said, adding that his life was not in danger.

The tiny west African state has been in the grip of a power struggle since August 2015, when Vaz sacked then premier Domingos Simoes Pereira, leader of the African Party for the Independence of Guinea and Cape Verde (PAIGC).

A new prime minister, Umaro Sissoco Embalo, was sworn in last December but PAIGC rejected him, accusing Vaz of breaching an agreement calling for a consensual choice of prime minister.

Last week members of Monteiro's group were badly beaten by police during a protest march, attended by PAIGC officials.

"The struggle will continue despite these attacks on our members," Sana Cante, the movement's coordinator told AFP.