DAKAR, Senegal (AP) — A Gambian political activist has died in detention after participating in a peaceful protest, Amnesty International said Saturday, calling for an investigation into the death and the release of others held.

Solo Sandeng, the opposition United Democratic Party’s organizing secretary, was arrested during a protest Thursday in Serrekunda that called for electoral reforms, the group said. The circumstances of his death are unknown. Sandeng was previously arrested in 2013 for his political activities.

Police dispersed the mostly peaceful protest and detained other opposition party demonstrators including Fatoumata Jawara, the president of the party’s female youth wing, who is believed to be suffering from serious injuries, Amnesty said.

The tiny West African nation is bracing for presidential elections in December 2016. Opposition parties and pro-democracy groups are demanding political and electoral reforms.

“Gambia must uphold the rights to freedom of expression and peaceful assembly, especially in advance of the elections,” said Amnesty. “All of the peaceful protesters arrested by the authorities should be immediately and unconditionally released. Any who are injured must receive urgent medical treatment.”

The government appointed a former stalwart of the ruling Alliance for Patriotic Reorientation and Construction as the new chair of the Independent Electoral Commission.

“These protesters come from different political backgrounds and their demands are very simple and legitimate,” said Alkali Conteh of Gambia Democracy Action Group. He also called on authorities to release demonstrators.

Protests against President Yahya Jammeh, whose rule since 1994 has been marred by human rights violations, are rare. Paramilitary forces gunned down 14 students who took part in a peaceful demonstration against Jammeh in April 2000.

Rights groups have also been calling for the release of journalist Alagie Abdoulie Ceesay, who has been detained since July.

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AP writer Abdoulie John in Dakar, Senegal contributed to this report.

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