* Boko Haram is Nigeria's top security threat
* At least 2,800 killed since insurgency began in 2009
MAIDUGURI, Nigeria, Nov 16 (Reuters) - Nigerian security forces said on Friday they had killed a top commander of Islamist sect Boko Haram in its northeastern stronghold during an offensive that also saw several other militants slain.
Boko Haram's insurgency, aimed at carving out an Islamic state in northern Nigeria, has killed an estimated 2,800 people since an uprising in 2009.
A recent military offensive has reduced the kind of lethal, high profile attacks they were carrying out a year ago, but there are still near daily assaults on civilians and security forces in the northeast.
"Ibn Saleh Ibrahim was killed alongside his foot soldiers in an offensive attack by combined forces ... with helicopters and amoured carriers," spokesman for joint military and police forces in Maiduguri Sagir Musa told Reuters.
He did not know the precise number of militants killed but said that the military had not taken any casualties.
Boko Haram is now the biggest security threat to Africa's biggest oil exporter and Western diplomats say it has established growing links with other jihadist groups in the region, including al Qaeda's north African wing in neighbouring Niger and Mali.
Musa said Ibrahim was behind the assassination of retired General Mamman Shuwa, a key figure in the 1960s civil war who was shot dead on Nov. 2 in Maiduguri, the capital of northeast Borno state, on the threshold of the Sahara, and the nucleus of the insurgency.
Nigerian security officials often trumpet their successes in offensives against Boko Haram but have been accused of down playing their own casualties and the deaths of civilians in clashes. The Islamists only rarely give their side of the story.
Witnesses reported that Nigerian troops shot dead at least 30 people during raids in Maiduguri two weeks ago. Amnesty International this month accused both sides in the conflict of killing civilians.
The military has claimed a number of successes against Boko Haram in recent months, including the killing of its spokesman and senior ideologue Abu Qaqa in an attack on his vehicle in September. (Reporting by Ibrahim Mshelizza; Additional reporting by Isaac Abrak in Kaduna; Writing by Joe Brock; Editing by Tim Cocks)