United Nations (United States) (AFP) – UN Secretary-General Ban Ki-moon on Sunday called on Gambia to thoroughly investigate the death in detention of opposition activist Solo Sandeng and two other party members.

Ban “learned with dismay” of the deaths after Sandeng and dozens of opposition members were arrested Thursday for taking part in a peaceful protest in the capital Banjul, a statement from his spokesman said.

Sandeng had recently been promoted to organizing secretary of the opposition United Democratic Party (UDP).

UDP leader Ousainou Darboe confirmed Sandeng’s death to AFP on Saturday and said two women who were also detained were in a coma.

The UN statement did not release details of the two other activists who also died in custody.

Ban “calls on the authorities to conduct a prompt, thorough and independent investigation into the circumstances that led to their death while under state custody,” said the spokesman.

Expressing deep concern about the “apparent use of excessive force and the arrest” of peaceful demonstrators, Ban called on the government to “immediately and unconditionally” release all those arrested including leader Darboe, who was hauled away by police during a second round of demonstrations on Saturday.

President Yahya Jammeh must “uphold the rights of the Gambian people to freedom of expression and peaceful assembly,” he added.

A military officer and former wrestler, Jammeh has ruled the west African country since he seized power in a coup in 1994, and is regularly accused of human rights abuses.

During the protest on Thursday, Gambian security forces beat dozens of UDP activists, rounded them up and took them to an unknown location.

Sandeng was taken away separately from his colleagues. He had previously been detained by the authorities in 2013, according to Amnesty International.