Sierra Leone's former president is headed to Nigeria for medical treatment despite being due to stand trial for his alleged role in a coup attempt last year.

Ernest Bai Koroma was permitted to leave by the High Court on Wednesday for a maximum of three months.

Sierra Leone's current president has called this a "humanitarian gesture".

But it is widely believed that a deal has been reached allowing Mr Bai Koroma to go into exile.

His treason trial is due to start in March.

Mr Bai Koroma led Sierra Leone for 11 years until 2018, when current President Julius Maada Bio was elected.

A Nigerian presidential jet carrying the former president was seen leaving Freetown International Airport on Friday afternoon.

The plane took off at about 13:30 GMT

Anonymous sources from the United Nations and Ecowas, a bloc of West African countries, have told the BBC that Ecowas had brokered a deal for Mr Koroma to go into exile in Nigeria if the charges were dropped to ease tension following the November unrest.

The BBC has also seen a letter saying Mr Koroma had agreed to the deal, which would see him continue to enjoy the perks of a former president even while he was in Nigeria.

In a nationwide address on Thursday night, President Julius Maada Bio said the issue of his predecessor was entirely in the hands of the judiciary.

"The courts have, therefore, granted the application for the former President to depart from the country purely for specialised medical reasons, and his trial will be suspended for the duration of his absence," he said.President Bio said it did not in any way detract from the seriousness of the ongoing trials, and that it was further proof that "the trial is not a political witch-hunt but one aimed at unravelling the truth behind the events of 26 November".

That attack saw armed assailants storm a military barracks and prisons, freeing around 2,000 inmates, the authorities said. At least 21 people were killed in the violence.

The government said this amounted to an attempt to overthrow it, and in subsequent weeks more than 80 people were arrested as suspects - many of them belonging to Sierra Leone's military.

The former president's daughter, Dankay Koroma, has previously been named on a list of suspects wanted by police investigating the failed coup. She has not commented.

The attempted coup came five months after a disputed election which saw President Bio narrowly re-elected for a second term.

The results were rejected by Mr Koroma's All People's Congress. International observers also criticised the elections, highlighting a lack of transparency in the count.