Updated

Amnesty International is calling on Gambia to investigate the death of an activist who it says died in detention after participating in a peaceful protest.

The rights group said Saturday that Solo Sandeng, of the opposition United Democratic Party, died after his arrest Thursday at a protest in Serrekunda. It said the circumstances of his death are unknown. Sandeng was previously arrested in 2013 for his political activities.

The group called on the government to release others arrested for participating in the demonstration that called for electoral reforms. It said another opposition member is believed to be suffering from injuries.

The tiny West African nation is preparing for December 2016 presidential elections. Opposition parties and pro-democracy groups are demanding electoral reforms which they say will encourage free and fair elections.