* Two men killed were on most wanted list - army
* Boko Haram pose biggest security threat to OPEC member
* Insurgency weakened but unlikely to be stopped - experts
By Imma Ande
YOLA, Nigeria, Aug 14 (Reuters) - Nigerian soldiers killed two top commanders of the Islamist sect Boko Haram during a four-hour gun battle in northeast Adamawa state, the military said on Wednesday.
Mohammad Bama and Abubakar Zakariya Yau were arrested near the town of Mubi last week and confessed they planned an operation in Taraba state to the south, Mubi Army Chief Beyidi Marcus Martins told reporters.
The men, who had bounties of 10 million naira ($62,200) on their heads, died in a gun battle that erupted after they took army officers to show them their hideout in Mubi. Several other sect members were also killed, Martins said.
There was no independent confirmation of the circumstances surrounding the men's death and Boko Haram has not commented publicly on the loss of its commanders.
Human rights groups have accused Nigerian soldiers of carrying out extra-judicial killings during their fight against Boko Haram. The army has always denied the accusations.
Boko Haram, which wants to impose sharia law in Nigeria's north, and other spin-off Islamist groups have become the biggest threat to stability in Africa's top oil exporter.
In mid-May, President Goodluck Jonathan declared a state of emergency and launched an offensive against the group in its stronghold in Borno, Yobe and Adamawa states in the northeast.
The insurgency, which has killed thousands since it intensified more than two years ago, was initially weakened but remains active and guerrilla-style attacks persist.
Suspected Boko Haram gunmen killed at least 44 people and wounded 36 after an attack during early Sunday prayers at a Mosque in northeast Borno state, which borders Adamawa to the north. The death toll rose from 30 initially.
Boko Haram's main target is security forces or government officials but it has carried out several attacks on Christian and Muslim worshippers, as well as schools and markets.
The group's leader, Abubakar Shekau, said in a video distributed to journalists on Monday that the army was lying about successes against his fighters, who had "killed countless soldiers" in recent weeks and would kill more.
"Despite the numerous arrests of suspected terrorists and continuous reports of the success of military offensives, there are still legitimate concerns over whether the ongoing security operations could really result in the resolution of the insurgency," a security source told Reuters on Wednesday. ($1 = 160.6 Nigerian naira) (Additional reporting by Lanre Ola in Maiduguri; Writing by Joe Brock; Editing by Jon Boyle)