* Boko Haram attacks military base in northeast with RPGs
* Struggle for an Islamic state has killed thousands
* Attacks radiating away from northeastern heartlands (Adds attack on military base, background, byline)
By Lanre Ola
MAIDUGURI, Nigeria, June 5 (Reuters) - A suicide bomber targeting worshippers at a mosque in a remote village in northeast Nigeria killed five people and wounded dozens, a security source said on Saturday, in an area where Islamist insurgents are mounting attacks almost daily.
The source, who declined to be named, said Muslims in the village of Konduga, in the northeasterly Borno state, were observing Friday prayers when the pick-up truck approached.
A local vigilante group stopped the truck to inspect it and the bomber then detonated the bomb a few metres away from the mosque, he said. There was no immediate claim of responsibility, but the Islamist group Boko Haram is likely to be the prime suspect.
In a separate attack, also on Friday evening, insurgents fired on a military base in the northeastern town of Damboa with rocket-propelled grenades, Gideon Jubrin, police spokesman for Borno state, said. He had no information on casualties.
Another security source said the raid was a revenge mission after dozens of Boko Haram militants were killed in an air and ground offensive on two of their camps in areas of Borno called Yejiwa and Alagarno.
Witness Mohammadu Sheriff, speaking of the attack in the village of Konduga, said he had seen the vigilantes conducting checks on a pick-up van carrying firewood.
"Suddenly it exploded," he told Reuters by phone. "It would have been more devastating if the bomber had succeeded in driving near the mosque, which had over a thousand people in it."
The Islamist militant group Boko Haram has killed many thousands since launching an uprising in 2009, and several hundred in the past two months, as it has stepped up a campaign against civilians in the northeast.
The militants, who are fighting for an Islamic state in religiously mixed Nigeria, see all who do not subscribe to their austere brand of Sunni Islam as enemies and often attack mosques as well as churches, especially if regarded as too moderate.
They have become by far the biggest security threat to Africa's most populous country, largest economy and leading energy producer.
The kidnapping of more than 200 schoolgirls by Boko Haram from the village of Chibok in April made world headlines. Despite pledges of Western support and promises by President Goodluck Jonathan to free them, they remain in captivity.
A spate of bombings across the north and centre of Nigeria in the past three months has also demonstrated the rebels' ability to strike outside of their northeastern stronghold. (Writing by Tim Cocks; Editing by Kevin Liffey and Stephen Powell)