MAIDUGURI, Nigeria — Army troops traded fire with Islamic militants Tuesday and deployed armored vehicles to surround the suspected hideout of a radical Muslim leader accused of orchestrating three days of violence in Africa's most populous nation.
A tense calm returned to several towns elsewhere in northern Nigeria after authorities imposed curfews and poured security forces onto the streets to quell a wave of militant attacks against police, which have killed dozens of people since Sunday.
Appealing for calm, President Umaru Yar'Adua told reporters: "This situation is being brought under control."
Sporadic gunfire was reported through the day in Maiduguri, capital of Borno state, where some of the worst violence occurred Monday. Police exchanged intermittent fire with militants as they tried to raid their camps in the city, according to local journalist Olugbenga Akinbule. He said more than 3,000 people had been displaced in the city.
Later in the day, the army sent armored vehicles to Maiduguri and deployed them in a residential district that is believed to be a stronghold of the sect. Officers said they believed militant leader Ustaz Mohammed Yusuf was holed up in a house in the district.
As army vehicles approached and opened fire, sect members fired back, soldiers said. An Associated Press reporter in the area saw smoke billowing above homes.
Army Maj. Gen. Saleh Maina said troops were hunting for sect members in homes and a mosque and near the Maiduguri railway station. He said the operation was being carried out "to prevent further loss of lives and property."
Troops and police had begun blocking off the area Monday, sealing streets and ordering residents to leave for their own safety. Elsewhere in the city, the bodies of dozens of dead militants lay on roadsides.
National police chief Ogbonnaya Onovo said Monday at least 55 people have died in the violence since it began Sunday, including 50 militants and five police officers. His spokesman Emmanuel Ojukwu said Tuesday authorities were still adding up the number of dead and arrested, and declined to give total figures.
Nigeria's 140 million people are nearly evenly divided between Christians, who predominate in the south, and primarily northern-based Muslims. Shariah was implemented in 12 northern states after Nigeria returned to civilian rule in 1999 following years of oppressive military regimes. More than 10,000 Nigerians have died in sectarian violence since then.
The radical sect behind the latest violence is known by several different names, including Al-Sunna wal Jamma, or "Followers of Mohammed's Teachings" in Arabic, and "Boko Haram," which means "Western education is sin" in the local Hausa dialect. Onovo referred to the militants as Taliban, although the group has no known affiliation with Taliban fighters in Afghanistan.
The group, which wants to see traditional government replaced by a Taliban-style state based on a strict interpretation of Shariah law and the Quran, first gained notoriety with a similar wave of assaults on New Year's Eve 2003. More attacks followed in late 2004.
Analysts say trouble has brewed for months, as police began raiding militant hideouts and finding explosives and arms.
Yar'Adua said the Islamic militants had been "preparing arms, learning how to make explosives and bombs to disturb our peace and force their ideas on the rest of Nigerians."
"Luckily, our security forces have been tracking them for years and I believe that the operation we have launched now will be an operation that will contain them once and for all," he said, referring to Maiduguri.
"What we have now is the situation in Borno state where the leader of the so-called Taliban group is resident, where most of them have migrated from all over the northern states to prepare, and declare a holy war," Yar'Adua said.
The president also said security forces would continue "security surveillance all over the northern states to fish out any remnants of these elements and deal with them."
The latest violence began Sunday in the northern city of Bauchi and spread the next day to three other predominantly Muslim northern states.
Mohammed Maigari Khanna, a spokesman for the governor of Bauchi state, said security forces Tuesday were searching for militants who had tried to flee and had arrested some of them. He said a dusk-to-dawn curfew had been imposed and security agents had blanketed the area.
In Kano state's Wudil district, where militants on Monday attacked a police station, 17 people were arrested overnight, bringing the total detained there to 53, according to Kano police spokesman Baba Mohammed. He said Kano was calm and police reinforcements had arrived to back up local security forces.