The Nigerian army says it has killed nine suspected members of extremist militant group Boko Haram in the northeast of the country.

"In a midnight encounter with Boko Haram insurgents, troops of the 7 division Nigerian Army killed nine Boko Haram terrorists while others fled with various degrees of injuries," AFP quoted army spokesman Colonel Muhammad Dole as saying in a statement issued on Friday.

Dole said that one soldier was also wounded in the clashes that occurred in Damboa area of Borno state late Thursday.

"During the encounter, arms and ammunitions were recovered and two pick-up vehicles were destroyed," he added.

On May 15, the Nigerian army launched an offensive against the militant group a day after President Goodluck Jonathan declared a state of emergency in three northeastern states of Borno, Yobe, and Adamawa.

Boko Haram -- whose name means “Western education is forbidden” -- says its goal is to overthrow the Nigerian government.

The group has claimed responsibility for a number of deadly gun and bomb attacks in various parts of Nigeria since 2009.

Over the past four years, violence in the north of Africa’s most populous country has claimed the lives of 3,600 people, including killings by the security forces.