More than a dozen soldiers area are said to have been killed in an ambush in the area where the army has been fighting armed groups.

Military sources were quoted by the AFP news agency as saying that at least 26 members of the Nigerian security forces were killed and eight wounded in the attack on Sunday.

Local media in Nigeria, however, reported that at least 13 soldiers had been killed in the ambush.

According to the AFP news agency, the rescue helicopter had been carrying 11 of the dead and seven of the wounded before the crash.

Rescue operations and investigations were under way, an air force spokesman has said, without giving information on casualties from the crash.

“The aircraft had departed Zungeru Primary School en route for Kaduna but was later discovered to have crashed near Chukuba Village in Shiroro Local Government Area of Niger State,” Edward Gabkwet said.

Armed gangs are common across central and north-west Nigeria where they rob and kidnap for ransom, and thousands of people have been killed in attacks in recent years.