Nigeria's police said on Tuesday they had arrested suspected members of an Islamist sect behind coordinated attacks in the north of the country that killed at least 65 people late last week.

Militants Boko Haram said they had carried out the gun and bomb attacks in Damaturu on Friday in the group's deadliest onslaught since it began a violent campaign for more widespread adoption of sharia law across Nigeria in 2009.

Residents expressed anger that gunmen were able to take over the city with apparent ease, leaving bodies littering the streets and reducing police stations, churches and mosques to rubble.

Persons have been arrested ... we are not at this time able to talk about who, or how many, or how they are linked to the incidents, said National Police Spokesman Yemi Ajayi.

Police say 53 people were killed but an emergency relief agency that counted bodies in morgues put the toll at 65 dead -- 63 from the Damaturu attack and another two from a strike on a neighbouring village.

On Sunday the U.S. embassy in Abuja issued a warning to its citizens to avoid hotels in the Nigerian capital, which it said could be targeted in coming days.

Boko Haram is becoming a major headache for President Goodluck Jonathan's administration as it grows in sophistication and deadliness. It has twice struck the capital this year.

Suspected members of the group, whose name means Western education is forbidden in local Hausa, shot dead an off-duty police officer on Sunday as he returned from Muslim prayers, police said.

Friday's violence also included a spate of bomb attacks in Maiduguri, the sect's home base and capital of Borno state which sits in the remote northeast. Police have not said if anyone died in those blasts.

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