LAGOS, May 14 (Xinhua) -- At least 72 hostages held by the extremist group Boko Haram have been rescued by the Nigerian army in several military operations in the northeastern state of Borno, a military source told Xinhua Wednesday night.

The abducted, mostly women and children, were freed after the troops completed the raids that have been launched since May 4 in some Boko Haram camps in Borno State in northeastern Nigeria, according to the source who declined to be named.

At least 18 Boko Haram members were killed, and many escaped with gunshot wounds during the operations, the source added, noting that a large cache of arms and ammunition, logistics supplies, and other equipment were recovered, and Boko Haram terrorists' collaborators were also captured.

Boko Haram's over-a-decade violent insurgency has posed a great security threat to Nigeria and its neighboring countries, causing thousands of deaths and displacement of millions of people since 2009.