The Nigerian Air Force (NAF) has completed the upgrade of four of its 24 Alpha jet trainers, and will soon re-enter them into service.

NAF chief of air staff (CAS) Air Marshall Mohammed Umar said that the jets had been reactivated in an effort to ensure combat readiness.

The four jets were upgraded by a firm in Germany and are currently stationed at their home base in Kainji, Kogi State, Nigeria.

The upgrade of the four aircraft was delayed due to lack of funds, according to Defenceweb.com.

The Air Force has been upgrading and modernising its equipment for the past few years, and has not disclosed if the NAF will upgrade its other 20 Alpha jets.

Nigeria has received 15 Chengdu F7s from China, comprising 12 F7-Ni fighters and three FT-7NI trainers to replace its grounded MiG-21s.