A human rights group is demanding that Equatorial Guinea release a human rights activist who was detained for denouncing the arrest of an opposition leader.

Amnesty International says Luis Nzo was beaten and then arrested on Thursday in the tiny, oil-rich Central African nation for distributing leaflets and using a megaphone to deplore the arrest of Guillermo Nguema.

Nguema, leader of the Republican Democratic Force opposition party, was arrested earlier in the week and taken to a village in the country's far east.

Equatorial Guinea is home to Africa's longest serving strongman, President Teodoro Obiang, who came to power through a military coup in 1979. It has the highest per capita income in Africa but its oil money benefits only a small elite and Obiang stifles the opposition.