* President says situation under control

* Security forces to flush out remaining rebels

* Death toll rises above 150, thousands displaced

(U.N. Sec-Gen, paragraph 12, arrests in Sokoto, paragraph 15)

By Ibrahim Mshelizza

MAIDUGURI, Nigeria, July 28 (Reuters) - Nigerian President Umaru Yar'Adua said on Tuesday that security forces would hunt down remnants of a radical Muslim sect behind days of clashes which killed at least 150 people and displaced thousands.

Supporters of a militant Islamic preacher armed with machetes, knives, home-made hunting rifles and petrol bombs have attacked churches, police stations, prisons and government buildings in parts of the mostly-Muslim north in recent days.

The violence was triggered when some members of the group called Boko Haram, which wants a wider adoption of Islamic sharia law across Africa's most populous nation, were arrested on Sunday in Bauchi state.

Unrest spread to the northern states of Kano, Yobe and Borno, whose capital Maiduguri is home to the group's leader, Mohammed Yusuf, and has seen the worst violence.

"The situation has been contained in Bauchi and Yobe. The bad situation we have now is in Borno where the leader of the group is residing ... We are going to launch an operation, a main operation to flush them out," Yar'Adua told reporters after meeting security chiefs and state governors.

"Our security agencies have been tracking them for years and I believe that this operation will be an operation that will contain them once and for all ... I assure you that the situation has been brought under control," he said before leaving for an official three-day visit to Brazil.

Yusuf is radically opposed to Western education -- Boko Haram means "education is prohibited". Critics say he has whipped some students as well as illiterate, jobless youths into an anti-establishment frenzy over a period of years.

Isa Azare, spokesman for Maiduguri police command, said 90 of the rioters as well as eight police officers, three prison officials and two soldiers had been killed in clashes with the security forces, causing hundreds of families to flee.

Scores of bodies were piled onto police trucks.

"When we heard shooting and saw people running we just packed the family and joined them," said Sunny Nwankwo, a journalist who fled to one of two barracks in Maiduguri sheltering thousands of civilians.

More than 50 people were killed in Sunday's violence in Bauchi and several have been reported killed in Kano and Yobe.

U.N. Secretary-General Ban Ki-moon said he was concerned by reports of "yet another round of sectarian violence".

JOBLESS YOUTHS

The four northern states are among the 12 of Nigeria's 36 states 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.

"We do not believe in Western education. It corrupts our ideas and beliefs. That is why we are standing up to defend our religion," a senior member of the group, Abdulmuni Ibrahim Mohammed, told Reuters on Monday after his arrest in Kano state.

Police in Sokoto state in the northwest said they had arrested Boko Haram's local leader, a former university lecturer, and four others found with cutlasses and knives.

Locals say Yusuf's views are not espoused by the vast majority of Nigeria's Muslim leaders or by their followers.

"I want to emphasise that this is not an inter-religious crisis," Yar'Adua said.

More than 200 ethnic groups generally live peacefully side by side in Nigeria, a country of around 140 million people, although civil war left one million dead between 1967 and 1970 and there have been bouts of religious unrest since then.

Radical Islamists -- dubbed the Nigerian Taliban after militants in Afghanistan -- launched a brief spate of attacks in late 2003 on police stations and government offices in the northeast, prompting a fierce security crackdown.

Security forces killed 25 suspected Islamic militants in an all-day battle on the outskirts of Kano in April 2007, days before a presidential election.

The State Security Services (SSS) arrested a group of Islamists with suspected links to al Qaeda around six months later and some Western diplomats have expressed concerns that Nigeria could become a target for radical Islamic groups.

But no conclusive evidence of al Qaeda's presence in Nigeria or of links to the Taliban in Afghanistan have been made public and Boko Haram's apparently chaotic tactics have little in common with those of Islamic militant groups elsewhere.

(For more Reuters Africa coverage and to have your say on the top issues, visit: http://af.reuters.com/ ) (Additional reporting by Mike Oboh in Kano, Ardo Hazzad in Bauchi, Felix Onuah in Abuja and Faruku Umar in Sokoto; Writing by Nick Tattersall; Editing by Giles Elgood)

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