The so-called Islamic State has confirmed that it carried out an attack in Nigeria that killed soldiers on Saturday.

Four soldiers including an army general died in the ambush attack in Borno state.

It's reported the army unit was on its way to reinforce troops engaged in a fierce battle with the insurgents.

Islamists have waged a devastating insurgency in the country's north-east for more than a decade.

President Muhammadu Buhari has expressed his sadness at the deaths of the soldiers, saying they paid the ultimate sacrifice to protect fellow Nigerians from terror.