A triple suicide bombing of military headquarters in Maiduguri and three roadside bombs in different areas shook northeast Nigeria's biggest city Friday, while militants launched multiple gun and bomb attacks two other cities west of it, witnesses and the military said.

It was one of the most violent days in radical Islamist sect Boko Haram's growing campaign of violence against local authorities in dry, dusty northeastern Borno state.

One soldier and six civilians have been injured by the three suicide bombers in multiple blasts, Lieutenant Colonel Hassan Mohammed, commander of the Joint Military Taskforce for Borno state, told Reuters.

Earlier, three roadside bombs exploded in quick succession in an apparently coordinated strike, hitting the wards of Meduguri and Jajeri and the El-Kanemi College of Islamic Theology, all of them around the time of Friday prayers, sending the Muslim faithful fleeing from their mosques.

The northeast's almost daily shootings and frequent bombings in the past months have been blamed on Boko Haram, whose name means Western education is forbidden. The attacks usually target public and religious figures in the poor, semi-arid north.

If the attack on the military headquarters is confirmed to be the work of Boko Haram suicide bombers, it will mark the second confirmed time the group have used this tactic.

The other was a suicide car bomb attack against the United Nations' Nigeria headquarters in Abuja, which killed 26 people and gutted several floors of the building.

Boko Haram says it wants sharia law more widely imposed across Nigeria. It draws much of its support from unemployed youths in the remote, economically deprived north.

The group appears to be growing in sophistication and security analysts believe it has made links with al Qaeda's north African affiliate -- al Qaeda in the Islamic Magreb.

A local security source said it was not yet clear if there were any casualties from the three bomb blasts in Maiduguri.

Suspected Boko Haram gunmen later attacked the towns of Damaturu and Potiskum, next to each other about 100 km west of Maiduguri, in Yobe state, and engaged in running gun battles with security forces, witnesses said.

Residents heard several explosions, which later turned out to be bombings of small local churches and a police stations, they said.

Several police stations and churches were bombed. The whole problem started around 6 p.m. this evening, when there was exchange of gun fire between the sect and the security operatives, said Damaturu resident Umar Gambo. It's horrible.

Another witness in Damaturu, a local journalist who declined to be named, said he had seen a group of 10 militants had attacked a mosque and the local police headquarters.

We are all indoors while the fighting is going on. Damaturu and Potiskum my home town are under siege. The Boko Haram sect have taken over the towns and the security men are battling them. No one is safe, said Potiskum resident Mammam Mohammed.

Security forces this week started door-to-door searches for weapons in the northeast, after an arms amnesty for Islamist militants expired on October 31. It was unclear whether or not this spate of attacks was a response to that operation.

(Reporting by a correspondent in Maiduguri and Mike Oboh in Kano; Writing by Tim Cocks; Editing by Alison Williams)