The leader of Nigerian Islamist group Boko Haram rejected peace talks with the government in a video on Sunday, distancing himself from a purported commander who declared a ceasefire on behalf of the sect in January.
The video was circulated to reporters in the northeastern city of Maiduguri, from where Boko Haram is waging a bloody insurgency against the state that has killed at least 3,000 people across northern Nigeria since 2009.
It came as troops killed 20 Boko Haram militants when they tried to attack the Monguno barracks in the northeastern state of Borno on Sunday, a security force spokesman said.
The video could not be immediately be verified, although the speaker appeared to be Abubakar Shekau, leader of the militant movement who has made several clips threatening the authorities or outlining the sect's position in the past.
A purported Boko Haram commander called Sheik Abu Mohammed Ibn Abdulazeez, who is known to Nigerian security forces, declared a ceasefire at the end of January.
The government cautiously welcomed it, but Shekau himself was silent and violence in the north has continued unabated.
"Abdulazeez has not been speaking on my behalf and I disassociate myself from him completely," Shekau said in the brief video in the northern Hausa language.
"(Boko Haram) has at no time offered a ceasefire and we are not in dialogue with government, neither are we prepared for it until the conditions we laid down have been met," he added, saying Nigerian security forces must stop killing the sect's members and calling them armed robbers.
Shekau's words raise questions about possible rifts within the secretive movement, which analysts say has splintered.
No one knows where Shekau is, and the security forces believe he was wounded in a gun battle with them late last year.
The Nigerian military often claims successes in clashes with Islamists, but rarely admits civilian deaths or significant casualties on its own side.
In a separate attack, gunmen shot and killed the police commissioner of the western state of Kwara, Chinweike Asadu, as he drove into his home, his spokesman Kwara Femi Fabode said.
It was not immediately clear whether the attackers were militants -- the area is just outside the known area of operations of Boko Haram -- or a criminal gang.
Western governments fear Boko Haram, or factions of it, has linked up with other groups in the region, including al Qaeda's North African franchise. Attacks in northern Nigeria are increasingly targeting foreign interests, especially since France's operation last month to flush Islamists out of northern Mali, to which Nigeria has committed hundreds of troops.
Gunmen killed a security guard and abducted a Briton, an Italian, a Greek and four Lebanese workers after storming the compound of Lebanese construction firm Setraco in Bauchi state on February 16.
That attack was claimed by Boko Haram splinter group Ansaru, which British authorities believe was behind the killing of a British and an Italian hostage last year.
Gunmen claiming to be from Boko Haram are holding a French family of seven seized from northern Cameroon.