Nigerian police hunt hundreds of escaped prisoners

He said the attackers "gained access and moved from cell to cell, breaking in and freeing the inmates. They set fire to a section of the prison and burnt the vehicles parked outside the gate."

One resident said the alleged sect members were chanting "Allahu Akbar" -- or God is great -- when they arrived.

Recent shootings blamed on sect members had signalled the group might be preparing to strike again in Africa's most populous nation, roughly divided in half between Christians and Muslims.

Last year's uprising began with attacks on police posts, and police were among the victims of the recent attacks by motorcycle-riding gunmen in northern Nigeria.

The 2009 uprising was crushed by a police and military assault, with hundreds eventually killed and the sect's headquarters and mosque left in ruins.

Tuesday's attack came on the same day officials announced January 22 as the date for Nigeria's presidential vote and was an ominous sign in a country where elections have often been tainted by violence.

Boko Haram means "Western education is sin" in local Hausa dialect, though the sect has been known by various names, including the Nigerian Taliban. It had fought for the creation of an Islamic state in Nigeria.