The United States of America has called on Gambia to immediately release all political prisoners after the reported death of another opposition member on Monday.

The U.S. State Department said in a statement on Monday night that it is deeply concerned by the death of the opposition member Ibrima Solo Krummah while in government custody.

“We remain troubled by reports of the Gambian government’s continued mistreatment of detained opposition figures, as evidenced by recent deaths and allegations of torture,” it added, calling for the humane treatment of all prisoners and the immediate release of all political prisoners.

- StateDept "deeply concerned" by death of #Gambia opposition member who was in gov't custody. pic.twitter.com/TQTCNX0Kl8 — Steve Herman (W7VOA) August 22, 2016

Gambia’s main opposition party, the United Democratic Party (UDP) announced on Monday the death of its member, Solo Krummah, who was arrested with over a dozen others in May after a protest against the death of another party official in April while in custody.

According to the party, he died shortly after surgery for an undisclosed ailment at the Edward Francis’s Small Teaching Hospital in the capital, Banjul on August 20.

Gambia-Another UDP member dead in Yaya Jammeh govt custody.Solo Krummah died shortly after surgery at govt hospital pic.twitter.com/CKfGANAki0 — UDPG ambia (@UdpGambia) August 21, 2016

The government and hospital authorities have not yet released official statements on the circumstances surrounding the Solo Krummah’s death.

The leader of the UDP, Ousainou Darboe, and 30 others were sentenced in July to three years in prison on several charges including unlawful assembly.

Their conviction comes five months before Gambia’s presidential election on December 1 which is expected to go in favour of the head of state Yahya Jammeh.