A Nigerian official says 4,000 people have fled their homes in the northern city of Maiduguri as troops and Islamist militants fight gunbattles for a fourth day.

The report comes a day after President Umaru Yar'Adua insisted the military had won control of the area.

National Emergency Management Agency spokesman Apollus Jediel says about 1,000 people fled their homes in Maiduguri on Wednesday alone. His agency is urging state governments to send relief goods to help the displaced people.

Militants seeking to impose Islamic Shariah law throughout this multi-religious country attacked a police station in Bauchi state on Sunday. The violence quickly spread to three other states.

Scores of people have been killed in the violence. Police say most of the dead are militants.

Olugbenga Akinbule, a local journalist, said he saw fighting Wednesday morning outside the suspected hideout of a radical Muslim leader accused of orchestrating three days of violence in Africa's most populous nation. He also said more people in the city of Maiduguri were fleeing, in addition to 3,000 people he said Tuesday had been displaced.

The military had surrounded the Islamic camp on Tuesday. Government officials did not answer calls seeking information on Wednesday.

Islamic militants attacked a police station in northern Nigeria on Sunday, sparking the worst violence Nigeria has seen in months and leaving at least 55 people dead over the next few days, according to police.

Maiduguri, capital of Borno state, has been the epicenter of the dayslong violence. Authorities imposed curfews Tuesday night and security forces poured onto the streets to quell a wave of militant attacks against police.

"This situation is being brought under control," Yar'Adua told reporters Tuesday as he appealed for calm.

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 militants oppose western education and seek a harsh interpretation of Islamic Shariah law in northern Nigeria.

Yet at the heart of the Islamic insurgency that sparked this week's violence is dire poverty and political maneuvering — not religion. The attacks on police have been committed by frustrated, unemployed youths and orchestrated by religious leaders and politicians who manipulate them to retain power.

Nigeria should be wealthy due to its prodigious oil reserves, but corruption and inefficiency have left many people in poverty. Despite promises of reform, Yar'Adua's government, like previous Nigerian governments, has failed to deliver even basic services like running water, electricity and health care.

Late Tuesday, the army sent armored vehicles to a residential district in Maiduguri that is believed to be a stronghold of an Islamic sect behind the violence. Officers said militant leader Ustaz Mohammed Yusuf was thought to be holed up in one of the houses.

As army vehicles approached and opened fire, sect members fired back, soldiers said. An Associated Press reporter in the area saw smoke billowing above the homes.

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.

Some Nigerian officials have referred to the militants as Taliban, although the group has no known affiliation with Taliban fighters in Afghanistan.