Nigeria's Foreign Minister Yusuf Tuggar has formally apologised to Burkina Faso for the unauthorised entry of a Nigerian military jet into Burkinabè airspace, an incident that led to the detention of 11 Nigerian servicemen.

Tuggar's spokesperson told the BBC that the detained personnel had been released and were due to return to Nigeria, without saying when.

The plane was flying to Portugal when it developed a technical problem and had to land in Burkina Faso, according to the Nigerian Air Force.

The unauthorised landing sparked a diplomatic row with the Alliance of Sahel States (AES) made up of Burkina Faso and its neighbours, Mali, and Niger.

In a statement, AES characterised it as an "unfriendly act" and said member states‘ respective air forces had been put on maximum alert and authorised to "neutralise any aircraft" found to violate the confederation's airspace.

The three AES states, all run by the military, have withdrawn from the West African regional bloc, Ecowas, and moved closer to Russia, while most Ecowas members remain allied to the West.

Tuggar led a delegation to the Burkinabè capital, Ouagadougou, on Wednesday, to discuss the incident with military leader Captain Ibrahim Traoré.

"There were irregularities concerning the overflight authorisations, which was regrettable, and we apologise for this unfortunate incident," Tuggar said on national TV.

It remains unclear when the military personnel, said to be in "high spirits", and the aircraft will return to Nigeria.

According to Nigeria's foreign ministry, both sides agreed to "sustain regular consultations and pursue practical measures to deepen bilateral cooperation and regional integration".