FREETOWN/ABUJA - Sierra Leone's ex-president Ernest Bai Koroma left the West African country by plane and flew to Nigeria on Friday, two Reuters reporters said, after a court allowed him to travel abroad on medical grounds despite treason charges.

On Jan. 3, 70-year-old Koroma was charged with four offences for his alleged role in a failed military attempt to topple the government in November, but a high court on Wednesday ruled he could leave the country.

The decision came amid concerns his indictment could stoke domestic tensions linked to the 2023 election, which saw President Julius Maada Bio reelected for a second term although the main opposition candidate rejected the results and international partners questioned the vote.

Koroma's lawyers have called the charges "trumped up" and part of a political vendetta.

A Reuters reporter at the airport in Sierra Leone's capital Freetown saw Koroma depart on a Nigerian presidential plane on Friday afternoon. The plane later landed in the Nigerian capital of Abuja and Koroma was greeted by Nigerian officials and the president of West Africa's political and economic bloc ECOWAS, a second Reuters reporter at the scene said.

ECOWAS did not immediately respond to a request for comment.

The president of the ECOWAS Commission, Dr Omar Alieu Touray, was in Sierra Leone last week, for the second time since the Nov. 26 coup last year, fuelling speculation the bloc brokered a deal with the Sierra Leone authorities to allow Koroma to relocate.

(Reporting by Umaru Fofana in Freetown and Felix Onuah in Abuja; Writing by Alessandra Prentice; Editing by Alison Williams)