Borno state police spokesperson Isa Azaza said police were holding 20 men suspected to be members of the Boko Haram sect. He said some of the men were seized with gunpowder, vats of acid, aluminum containers for bomb-making, assault rifles and black-and-white flags with Arabic inscriptions.

Azaza said the group was well organised in its attacks on police stations and government installations.

The city of Maiduguri was calm on Monday morning, with police conducting street patrols.

The radical group sparked the violence with a July 26 attack on a police station in Bauchi. Violence quickly spread to three other northern states.

36 suspects arrested in Nigeria

Police in Nigeria said they had arrested 36 suspected members of a radical Islamist sect after security forces crushed a violent uprising by the movement.

The independent newspaper Saturday Punch published a picture of the suspects, most of them young boys. Police said the suspects included two from neighbouring Niger.

"Thirty-six suspected members of the group, among them two nationals of Niger Republic, were intercepted and arrested... (on) July 30," according to a statement by Abuja police chief Haruna John.

The members of the group, known as Boko Haram, were arrested in Zuba, on the outskirts of the Nigerian capital Abuja, while travelling west on their way to Lagos, the commercial capital.

"Investigations reveal that all the 36 suspects left their different locations in Kano, Jigawa and Yobe - all northern states - to assemble in Kano before their planned movement to Lagos," John said in a statement read out to reporters on Friday by his spokesperson, Jimoh Moshood.

All the suspects will soon face charges in court after an investigation, he said.

Clashes this week between the sect members and security forces left more than 600 dead in the northern states of Bauchi, Kano, Yobe and Borno.

The sect's spiritual leader, Mohammed Yusuf, was shot dead in controversial cicumstances.

The acting inspector general of police, Ogbonnaya Onovo denied in a statement that Yusuf was killed while in police custody.

"This is not true," Onovo said. "The Nigeria Police Force restates that Mohammed Yusuf died in a crossfire with security operatives."