Burnt out vehicles and scattered rubbish is all that's left of this militant camp in northern Nigeria.

Since last month, government troops have stepped up efforts to stamp out insurgent groups that have plagued the oil-producing country and killed thousands over the last four years.

According to the military, this was one of several camps belonging to Islamist Boko Haram fighters.

A defence spokesman said the biggest offensive yet against the group was necessary and that so far it has proven successful.

(SOUNDBITE) (English) BRIGADIER GENERAL CHRIS OLUKOLADE, DEFENCE SPOKESMAN, SAYING:

"Every one who is carrying arms illegally in this country is a terrorist. Call them by whatever name and the operation is aimed at ensuring that no such activity of terrorism takes place within the territory of Nigeria. It is our time to assert the territorial integrity of Nigeria as a country."

Nigerian President Goodluck Jonathan declared a state of emergency in thre