* Islamist violence has surged over past two months
* President ordered operation in May to crush rebellion
* Under pressure from party split and opposition coalition
Nigeria's military said on Wednesday it had killed 150 insurgents, including a commander named Abba Goroma, in an operation against Islamist group Boko Haram in which 16 of its own forces were also killed.
Violence in northeast Nigeria has intensified over the past two months, as the Islamists fight back against a military operation that president Goodluck Jonathan ordered in May to try to crush their four-year rebellion.
Army spokesman Brigadier General Ibrahim Attahiru said a series of raids carried out on Islamist camps in northeastern Borno state had pushed Boko Haram into hiding in a forest.
He said they had received intelligence reports on Sept. 12 that they were planning to launch an attack from there, adding that they were "well fortified with anti-aircraft and anti-tank guns mounted on vehicles".
"Based on this report, our own troops launched a deliberate attack. Over 150 insurgents were killed and the formation lost an officer and 15 soldiers," he said.
Attahiru was quoted in local newspapers on Wednesday as denying a story on Nigeria's Premium Times website that Boko Haram had killed 40 soldiers in an ambush in the same area.
The Nigerian army often says large numbers of insurgents have been killed in a battle in which a much smaller number of its own troops died. It is impossible to independently verify the numbers, although witnesses often give higher figures for troop casualties than the official ones.
No witnesses were immediately contactable in the area.
Boko Haram, whose name means "Western education is sinful", wants to revive an era of medieval Islamic kingdoms in religiously mixed Nigeria by creating a breakaway state that would follow strict sharia law.
It is seen as the gravest security threat to Africa's top oil producer. Although their activities are located hundreds of miles away from its southern oil fields, they have bombed the capital Abuja at least three times, including a deadly attack on the United Nations' Nigeria headquarters in 2011.
Thousands of people have been killed since the shadowy sect launched its uprising against the state in 2009, transforming from a clerical movement opposed to Western culture to an armed insurrection with growing links to al Qaeda's West African wing.
The army said on Sept. 12 that it had killed 10 insurgents, and a week earlier said it killed 50 of them.
Surging violence in the northeast is unwelcome news for Jonathan, who is under intense political pressure due to a split in his party and from a recently formed opposition coalition.
He had been criticised for not quelling Boko Haram's insurgency, which worsened under his leadership, and the state of emergency he declared in May was seen as last ditch attempt.
The military said last month Boko Haram's leader Abubakar Shekau may have died in late July of wounds inflicted during a gun battle. If true, it has failed to end the violence.