Suspected Islamic sect members ambushed and killed at least 24 members of a youth vigilante group who were on a mission to find and fight the sect in northeast Nigeria, a security official said Saturday.

Those who returned from Friday's attack told officials that 36 other vigilantes were missing, the official said on condition of anonymity because he is not permitted to speak to the media.

"The vigilante youths numbering over 100 were on a mission to capture some Boko Haram terrorists in their camps around Kaleri, Shuwari, Maganari and Nannari villages around Monguno's local government area, before they were ambushed by the terrorists," he said.

The attack took place somewhere near Monguno town, 160 kilometers (100 miles) from the city of Maiduguri, the Borno state capital where the Boko Haram ideology sprang up some four years ago.

The vigilante group, known as the Civilian Joint Task Force, said its attackers were wearing military uniforms. The official said the Civilian-JTF usually gets a military escort when it goes on a search mission but that when the military did not arrive on time the vigilantes headed out.

They later told officials they saw three patrol vehicles painted in camouflage and approached them thinking they were the escorts. The sect members then opened fire, killing at least 24 Civilian-JTF members, the security operative said.

The Civilian-JTF has recently become a target for Boko Haram, an armed Islamic group that has been waging a bloody war in Africa's most populous nation. Two attacks — one earlier in the week and the other last weekend — killed at least 20 members of the vigilante group, residents and an official said.

"We are getting too many attacks and our members' deaths are on the rise. I am scared, and so are some of my friends in the vigilantes," said Shehu Ibrahim, a member of Civilian-JTF. "We may back out if we are not protected."

The state's foremost monarch, the Shehu of Borno, Abubakar Garbai Alamin El-Kanemi, had requested financial and material support for the Civilian-JTF while attending a government meeting in the troubled city of Maiduguri.

The Civilian-JTF group has taken over in the search for the insurgents in the city, and most Boko Haram members have since relocated to the surrounding bushes, though they continue to kill locals. The vigilante force has arisen in northeast Nigeria as a backlash against Boko Haram, and the group claims credit for thousands of arrests in Maiduguri, where Boko Haram started.

Many residents welcome the vigilantes and credited them for some initial relative peace. Others find their existence troubling and worry that they may cause human rights abuses.