Nigerian President Muhammadu Buhari has has sent condolences to the families of seven soldiers who died in a plane crash in the capital, Abuja.

The authorities have launched an investigation into the crash.

The Nigerian Air Force said the families of all the victims had been informed of the deaths.

President Buhari described them as "dedicated and courageous".

The plane took off from Abuja and was headed to Minna, in the northern state of Niger, when it turned back following engine failure, according to the military.

It crashed short of a runway.