A radical Muslim sect in northern Nigeria claimed responsibility Wednesday for the assassination of a gubernatorial candidate and a series of other attacks, warning in posters put up around town that they plan to launch "a full-scale war."

The group known as Boko Haram already had been blamed for the killing of Modu Fannami Gubio, the Borno state candidate of the All Nigeria People's Party. The group also has been accused of carrying out motorcycle-mounted attacks against policemen in the area.

Boko Haram was thought to be vanquished in 2009 after Nigeria's military crushed its mosque into concrete shards, and its leader was arrested and died in police custody. But now, a year later, Maiduguri and surrounding villages again live in fear of the group. Western diplomats also worry that the sect is catching the attention of al-Qaida's North Africa branch.

The group's claim of responsibility for seven recent killings appeared in posters at the post office, railway station and other locales in Maiduguri on Wednesday.

"We are therefore, calling on Muslims in this part of the world to be wary because very soon, we would launch a full-scale war," it said.

"We also call on the people not to sit close to where security agents or politicians are living because such people are behind the illegalities being meted on the Muslims," the poster read.

However, Police Commissioner Mohammed Abubak cast doubt on their authenticity, saying the copies of the posters "are not genuine" and that the public should not panic.

It's not the first time such posters have been put up in the area with Boko Haram's message. In October, similar posters warned the public against assisting the police or going near soldiers guarding the town at night.

Those posters also bore a symbol of an opened Quran, flanked on each side by Kalashnikov assault rifles and a flag in the middle — mirroring the logo of al-Qaida in the Islamic Maghreb.

Boko Haram — which means "Western education is sacrilege" in the local Hausa language — has campaigned for the implementation of strict Shariah law. Nigeria, a nation of 150 million people, is divided between the Christian-dominated south and the Muslim north. A dozen states across Nigeria's north already have Shariah law in place, though the area remains under the control of secular state governments.

In December, Boko Haram claimed responsibility for the Christmas Eve bombings and church attacks in Nigeria that left dozens dead. Authorities said a Baptist pastor and two choir members preparing for a late-night carol service were among the victims.

The group also has been blamed for killing more than a dozen police officers and soldiers manning checkpoints since July.

Those recent attacks have shown accused Haram members' ability to kill at will despite a military and police crackdown, leaving a state police commissioner to acknowledge he cannot guarantee the safety of election officials.

The violence also comes ahead of April elections that many worry could ignite simmering ethnic and religious tensions in a country that became a democracy only a decade ago.