* More than 100 arrested in house-to-house raids
* Police say freed 180 women and children
* Sect leader's whereabouts unknown
(Adds arrests, women and children freed)
By Ibrahim Mshelizza
MAIDUGURI, July 29 (Reuters) - Security forces in northern Nigeria have freed nearly 200 women and children during a crackdown on a radical Islamic sect responsible for violence that has killed at least 150 people.
Soldiers in armoured personnel carriers surrounded and shelled parts of a compound that is home to Mohammed Yusuf, the leader of the radical Boko Haram sect, in the city of Maiduguri, destroying buildings including a small mosque.
The preacher's whereabouts were unknown. Joint military and armed police patrols went from house to house searching for his followers, arresting more than 100 people.
Police said they had freed 180 women and children whose husbands and fathers were among Yusuf's followers. Members of the sect say their wives should not be seen by other men and that their children should receive only a Koranic education.
"The soldiers and police are now combing the whole city of Maiduguri, going house to house searching for followers of the Boko Haram," Maiduguri resident Adamu Yari told Reuters.
"Hundreds of the members have been arrested," he said, adding that the sound of military bombardments from the area around Yusuf's compound had continued throughout the night.
Police in Kano, 500 km (310 miles) further west, said they had arrested 53 Boko Haram followers including the second in command in the state and said they were under orders to destroy the local leader's home and mosque.
They said the men had been found with home-made guns and explosives and were believed to be planning attacks. Arrests have also been made in Sokoto, in the far northwest.
President Umaru Yar'Adua has ordered the security forces to take all necessary action and warned that the leader of the group wants to declare a "fully fledged holy war".
"These people have been organised and are penetrating our society and procuring arms and gathering information on how to make explosions and bombs to force their view on the rest of Nigerians," Yar'Adua said.
"We are going to continue with security surveillance all over the northern states and fish out any remnant of this group and deal with them promptly."
MODELLED ON THE TALIBAN
The violence erupted when members of Boko Haram, which wants a wider adoption of Islamic sharia law across Africa's most populous nation, were arrested on Sunday in Bauchi state on suspicion of planning an attack on a police station.
Yusuf's supporters -- armed with machetes, knives, home-made hunting rifles and petrol bombs -- have since attacked churches, police stations, prisons and government buildings in four states across the mostly Muslim north.
Police in Maiduguri have said 90 of the rioters have been killed as well as eight police officers, three prison officials and two soldiers. More than 50 people were killed in the initial violence in Bauchi and several more have died in Kano and Yobe.
The states affected are among the 12 of Nigeria's 36 that started a stricter enforcement of sharia in 2000 -- a decision that has alienated sizeable Christian minorities and sparked bouts of sectarian violence that killed thousands.
Boko Haram, which means "Western education is a sin" in the Hausa language spoken across northern Nigeria, is loosely modelled on the Taliban movement in Afghanistan and is sometimes referred to as the "Nigerian Taliban".
Its followers -- who include some university lecturers and students as well as illiterate, jobless youths -- wear long beards and red or black headscarves and recognise only their own interpretation of sharia law.
"Poverty, injustice and the inability of the government of the day to implement the sharia legal system is the reason why the sect is calling for a change of leadership for Nigeria," Kadiru Atiku, the group's leader in Sokoto, told reporters after his arrest on Tuesday.
Such views are not espoused by the majority of Nigeria's Muslim population, the largest in sub-Saharan Africa.
More than 200 ethnic groups generally live peacefully side by side in the country of around 140 million people, roughly equally split between Christians and Muslims, although civil war left 1 million dead between 1967 and 1970 and there have been bouts of religious unrest since then.
The violence in the north is not connected to unrest in the Niger Delta in the south, where militant attacks have prevented Nigeria from pumping much above two-thirds of its oil capacity. (For more Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ ) (Additional reporting by Faruku Umar in Sokoto, Mike Oboh in Kano, Felix Onuah in Abuja; Writing by Nick Tattersall; Editing by Giles Elgood)