(Adds comments on Shekau, other details)
By Estelle Shirbon
LONDON, Jan 22 (Reuters) - Nigeria's campaign against Islamist Boko Haram insurgents is being hampered by "cowards" in its armed forces, its presidential security adviser said in a rare public sign of high-level unhappiness with the effort.
Boko Haram's bloody uprising to carve out a breakaway Islamic caliphate has seized much of Nigeria's northeast and poses the worst threat to Africa's most populous state and biggest energy producer and at least three of its neighbours.
Boko Haram claimed a Jan. 3 attack on the town of Baga that killed scores, possibly hundreds, of civilians and left the jihadists in control of the headquarters of a regional multinational force including troops from Niger, Chad and Cameroon.
Nigerian soldiers fled the area after Baga was overrun. It was the latest Boko Haram success to cast doubt on the commitment of some in the military, and 22 officers including a brigadier general are on trial over alleged sabotage in the war effort.
"Unfortunately we have a lot of cowards. We have people who use every excuse in this world not to fight," Sambo Dasuki, the top security adviser to President Goodluck Jonathan, told an audience at the Chatham House think-tank in London on Thursday.
But, he stressed, "there is no high-level conspiracy within the army not to end the insurgency."
Dasuki denied the army was under-equipped, as critics have asserted, calling this an "excuse."
He said of troops from Chad, Niger and Cameroon that were supposed to be stationed there at the time of the attack: "That wasn't that much of a multinational task force, it was by name (only), because they were all supposed to be physically there," when in fact most were not.
Dasuki added there was international pressure to set up a multinational task force with headquarters in the Chadian capital N'Djamena, but "Nigerians don't see what the use is" of the regional force.
Returning to the subject during his talk with journalists later, Dasuki said however genuine cooperation between the forces of all four nations was essential to defeat the insurgency.
Dasuki said the leader of Boko Haram, a mysterious figure known as Abubakar Shekau whom the Nigerian army have repeatedly claimed to have killed, remained in control of the insurgent group.
A man purporting to be Shekau claimed responsibility in a new video on Tuesday for the attack on Baga.
"We believe he is present at every major operation (of Boko Haram)," Dasuki said.
Dasuki added Shekau had travelled "all over the world" to receive training from other Islamist extremist groups. He named Pakistan and Mali as training grounds for Shekau and other Boko Haram fighters.
He said he estimated Boko Haram had about 5,000 active fighters. (Reporting by Estelle Shirbon and David Clarke; Writing by Tim Cocks; Editing by Andrew Roche)