A Nigerian military helicopter has crashed and exploded in Adamawa State, where Boko Haram conduct a rampant campaign of violence and intimidation.

The incident occurred in Damare, a suburb of Girei Local Government Area of Adamawa state, one of the three states most affected by Boko haram's activities.

A security source in the capital Abuja told Reuters that some casualties were reported but declined to give further details.

Who are Boko Haram?

Boko Haram, which fights against Western influence in Nigeria and aims to impose its version of sharia law in the country, declared an Islamic caliphate in Gwoza, along the Cameroon border, in August 2014.

The group has been raiding several cities in the north of the country in a bid to take control of more land.

Borno, Yobe, and Adamawa states, where the militants usually carry out their attacks, have been under a state of emergency since May 2013.

Violence linked to Boko Haram's insurgency has resulted in an estimated 10,000 deaths between 2002 and 2013.

However, the military sources confirmed that no one had died in the incident.

It was the second Nigerian military helicopter to go down this week in Adamawa State.

"It is true a helicopter just crashed near Mautech [Modibbo Adama University of Technology‎] at around 9:30 pm," a Yola resident told Nigerian newspaper Premium Times.

"There were actually two of them flying beside each other and when one crashed, the other one turned back."

Another witness said: "We came out of our hostel when we heard the sound of choppers and noticed that there were two of them flying in the dark without lights on.

"Suddenly one of them went down and exploded with a deafening sound. Immediately after that happened the other one turned back and left. Obviously there were explosives inside the chopper because intermittent explosions followed the fall of the helicopter creating a huge fire blast.

"Even as we speak, you can see the huge fire blazing from our hostel, although the explosions have abated a little.

The spokesperson of the Nigerian Air Force, Dele Alonge, an Air Commodore, confirmed the incident, but did not give further details.