* Boko Haram commander called for ceasefire
* Nigeria security forces will remain deployed (Adds presidency comments)
MAIDUGURI, Nigeria, Jan 29 (Reuters) - Nigerian authorities on Tuesday welcomed a ceasefire declaration by a commander of Islamist sect Boko Haram, but security forces said they would not lower their guard.
Sheik Abu Mohammed Ibn Abdulazeez, who security sources say is a Boko Haram commander, called on sect members on Monday to halt attacks that have killed many hundreds since it launched an uprising to carve out an Islamic state in Nigeria in 2009.
But it was not immediately clear if Abdulazeez was speaking on behalf of Boko Haram leader Abubakar Shekau, who has neither publicly backed nor denounced the commander - who also called for dialogue twice in November last year.
In a statement to journalists in Maiduguri, the sect's headquarters, Abdulazeez urged security forces to reciprocate.
The doubts over the authority of Abdulazeez raise questions about possible rifts within the secretive militant movement. He may represent only one Boko Haram faction.
"It is a good step for Boko Haram to be moving in the right direction. We wish it to become an all encompassing thing, rather than just a faction," presidency spokesman Doyin Okupe told a news conference in the Nigerian capital Abuja.
"I'm sure the government will discuss (its move) once it has been ascertained that it is genuine, that it is sincere."
Hours before Abdulazeez spoke, gunmen in Borno state killed eight people in an attack that bore the hallmarks of Boko Haram, but which could also have been a criminal gang profiting from the growing lawlessness in Nigeria's northeast, raising doubts about how much impact a ceasefire would have on security.
The sect's activities and associated insecurity are seen as the main security threat to Africa's leading energy producer.
"Conflicts are resolved through dialogue, hence the declaration of ceasefire by the sect's leader is a welcome development," Lieutenant Colonel Sagir Musa, spokesman for joint military and police forces (JTF) in Borno state, said by phone.
"Be that as it may, the JFT will remain in a staging position to continue maintaining law and order ... in its area of operational responsibility," he said.
The timing of the alleged ceasefire has been seen as curious given Nigeria's involvement in military efforts to dislodge Islamists in Mali, with whom Boko Haram are known to have forged links. Security agencies had been braced for a backlash.
A spokesman for Borno state governor Kashim Shettima also welcomed the ceasefire.
"The governor has regularly advocated that, unless we want to engage in an endless war, the best way out of the crisis is dialogue," his spokesman Isa Umar Gusau said.
President Goodluck Jonathan has alluded to links between Boko Haram and Saharan Islamists as a reason for joining efforts by allied French and West African forces fighting them in Mali.
But critics say Nigeria's insurgency is largely a home-grown problem that can only be resolved with a political settlement. (Reporting by Ibrahim Mshelizza in Maiduguri and Joe Brock in Abuja; Writing by Tim Cocks; Editing by Alison Williams)