MAIDUGURI (Reuters) - The leader of Nigerian Islamist group Boko Haram rejected peace talks with the government in a new 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.

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 films 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, listing those conditions as that Nigerian security forces must stop killing the sect's members and calling them armed robbers.

Shekau's comments raise questions about possible rifts within the secretive movement, which analysts say has long been splintered into different factions with varying interests.

No one knows where Shekau is, and the security forces believe him to have been wounded in a gun battle with them late last year.

Nigerian security forces killed 20 Boko Haram militants when they tried to attack the Monguno barracks in the northeastern state of Borno, a security force spokesman said. The Nigerian military often claims successes in clashes with Islamists, but rarely admits civilian deaths or significant casualties on its own side.

Western governments are concerned that Boko Haram, or some factions of it, have linked up with groups elsewhere in the region, including al Qaeda's North African franchise, especially given the conflict in nearby Mali, to which Nigeria has committed hundreds of troops.

Attacks in northern Nigeria are increasingly targeting foreign interests, especially since France's operation last month to flush Islamsists out of northern Mali.

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 a Boko Haram splinter group called 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.

(Reporting by Ibrahim Mshelizza; Writing by Tim Cocks; Editing by Jon Hemming)