Left-wing Cameroonian opposition figure Anicet Ekane has died in detention, five weeks after he was arrested, his lawyers and party have announced.

Ekane, 74, was among the leaders of an opposition coalition who endorsed Issa Tchiroma Bakary in October's presidential election.

Tchiroma Bakary says he was the rightful winner of the poll, officially won by 92-year-old incumbent Paul Biya. Tchiroma Bakary has since fled to The Gambia.

No official cause of Ekane's death has been announced. His party has accused the authorities of denying him access to his medication - a charge the government has denied.

According to a spokesman for Ekane's African Movement for New Independence and Democracy (Manidem) party, Ekane died on Monday morning at a military medical facility, after his health worsened over the weekend.

"We have no clarification... His wife had been called to come and when she found herself there, she was just presented the corpse of her husband," he said.

He added that the family later took the corpse to the mortuary.

Defence ministry spokesman Capt Cyrille Serge Atonfack said the Manidem leader had died from illness, but did not give any further details.

"The deceased, who suffered from various chronic pathologies, had been interned at the Military Medical Centre of the National Gendarmerie," he said, adding that the politician had been well taken care of by doctors since his arrest on 24 October.

According to Ekane's lawyers, he was accused of hostility against the state, incitement to revolt, and calls for insurrection.

"He was never presented before a judge or charged with any misdemeanour," said one of his lawyers, Hippolyte Meli, in a statement on social media, describing the detention of the Manidem party leader as "illegal".

In recent weeks, rumours had circulated that the opposition figure had died, and Ekane's party members had demanded to see him "dead or alive".

His death has sent shockwaves across the nation, with supporters gathering at the party headquarters in Douala to grieve. Others have taken to venting their anger online.

Manidem says its premises have been surrounded by security forces.

Ekane initially endorsed another vibrant opposition figure, Maurice Kamto, for the presidential election. But Kamto, who endured a long detention after disputing the previous election in 2018, had his candidacy rejected upfront this time by both the electoral body, Elecam, and the Constitutional Council, on the grounds that the party had endorsed more than one candidate.

Ekane and other politicians went on to create the Union for Change Coalition with other politicians, which named former government spokesman Tchiroma Bakary as its candidate.

Authorities say an investigation has been launched to determine the exact circumstances of Ekane's death.