In what could be the biggest catch ever since Africa's most populous nation launched a manhunt for top figures of the insurgency plaguing the country, Nigeria has claimed it arrested top militant Khalid Al-Barnawi. But the claim was denied in some quarters, with skeptics saying he remains at large. Al-Barnawi is the leader of the Ansarul-Muslimeen, a group just as deadly as Boko Haram militants but not as outspoken. Popularly called KAB, Al-Barnawi is a top Al-Qaeda operative trained in western North Africa's Maghreb. In June 2013, the US State Department designated Al-Barnawi, alongside Boko Haram chief Abubakar Shekau, as Specially Designated Global Terrorists. He is believed to have bankrolled the 2011 bombing of the UN office in the Nigerian capital city Abuja which killed at least 21 and wounded 60. Unlike Shekau, Al-Barnawi has not pledged allegiance to ISIS. His group has carried out deadly attacks in the northeast and across the Lake Chad region. Nigerian defense spokesman Brig. Gen. Rabe Abubakar confirmed to Anadolu Agency that security agencies have Al-Barnawi "in custody." Ahmad Salkida, a local journalist close to Boko Haram, supported the claim, saying the arrest was made in the north central Kogi state on Friday. But several sources close to the Ansarul-Muslimeen insist that Al-Barnawi "remains a free man." "Khalid Al-Barnawi has not been arrested. His people are calling the arrest claim [garbage]," top counterinsurgency expert Fulan Nasrullah told Anadolu Agency Sunday morning. "They [security agents] don't even know Al-Barnawi. They don't even know his real name. Nor do they know where he is from beyond that Al-Barnawi suggests a Borno origin," Nasrullah added, referring to a northeastern Nigerian state. He said the latest arrest claim is no different from previous claims of Al-Barnawi's death. "They announced his death at least seven times," according to Nasrullah. "They have different people's pictures that they label as him." A source in the country's Interior Ministry also denied that Al-Barnawi is in custody. "According to my sources, KAB is still roaming free," according to the source, who asked not to be named. "Remember this is the same person that the DSS [Department of State Service, Nigeria's domestic intelligence agency] and the military claim to have killed him many times in the past," he added.