Gun and bomb attacks by Islamist insurgents in the northern Nigerian city of Kano last week killed at least 178 people, a hospital doctor said on Sunday, underscoring the challenge President Goodluck Jonathan faces to prevent his country sliding further into chaos.

A coordinated series of bomb blasts and shooting sprees mostly targeting police stations on Friday sent panicked residents of Nigeria's second biggest city of more than 10 million people running for cover.

The scale of the carnage makes this by far the deadliest strike claimed by Boko Haram, a shadowy Islamist sect that started out as a clerical movement opposed to western education but has become the biggest security menace facing Africa's top oil producer.

"We have 178 people killed in the two main hospitals," the senior doctor in Kano's Murtala Mohammed hospital said following Friday's attacks, citing records from his own and the other main hospital of Nasarawa.

"There could be more, because some bodies have not yet come in and others were collected early."

The streets were quiet on Sunday in Kano, a vast metropolis of wide paved highways, normally buzzing with motorbikes, and sandy alleyways where hawkers sell grilled meat and donkeys pull carts heaped with fruit and vegetables.

Churches, which would usually be filled with worshippers in the religiously mixed city, were largely empty.

Jonathan, a Christian from the south, travelled to Kano on Sunday, visiting hospitals to speak to victims.

"Our coming today is to express our condolence to the good people of Kano over the dastardly acts," Jonathan said at the palace of the Emir, the city's Muslim figurehead.

"Those causing havoc will never succeed ... The federal government will not rest until the perpetrators are brought to book. We will not rest until these terrorist are wiped out," said Jonathan, wearing a traditional northern Nigerian kaftan and hat.

Boko Haram has been blamed for killing hundreds of people in increasingly sophisticated bombings and shootings, mostly targeting security forces, establishment figures and more recently Christians, in the country of 160 million people split roughly evenly between them and Muslims.

MORE ATTACKS ON SUNDAY

Apart from a handful of forays into the capital Abuja, the sect's energies have been concentrated in the majority Muslim north, far from the oil producing facilities along the southern coast that keep Africa's second biggest economy afloat.

A further 10 people were killed on Sunday in Bauchi state, which neighbours Kano, when police fought gunmen attempting to rob a bank, the police said. Boko Haram robbed several banks last year to fund its insurgency.

"In the early hours of today gunmen killed 10 people at a military checkpoint and a nearby hotel at Tafawa Balewa local government area," police commissioner Ikechukwu Aduba told Reuters.

"One police officer, an army corporal and eight civilians (were killed) after gunmen were earlier repelled from robbing a bank."

Explosions also struck two churches in Bauchi on Sunday, witnesses said, destroying one of them completely, although there were no immediate reports of casualties.

The government has announced a dusk-to-dawn curfew in Kano, an ancient city that was once part of an Islamic caliphate trading riches on caravan routes connecting sub-Saharan Africa with the Mediterranean.

Jonathan, who helped broker a deal that largely ended an insurgency by militants in the oil-rich southeast in 2009, has been criticised for failing to grasp the gravity of the crisis unfolding in the north, and of treating it as a pure security issue that will fizzle out by itself.

Worsening insecurity has led some to question whether Nigeria isn't sliding into civil war, 40 years after the secessionist Biafra conflict killed over a million people, though few think an all-out war splitting the country into two or more pieces is a likely outcome.

U.N. Secretary-General Ban Ki-moon condemned the attacks and called for "swift and transparent investigations" into the killings. European powers and the African Union have also condemned the attacks.

SECT CHANGING

Boko Haram became active around 2003 in the remote, northeastern state of Borno, on the threshold of the Sahara, but its attacks have spread into other northern states, including Yobe, Kano, Bauchi and Gombe.

Boko Haram, a Hausa term meaning "Western education is sinful", is loosely modelled on Afghanistan's Taliban, but analysts say the anger it channels reflects a perception that the north has been marginalised from oil riches concentrated in the south.

The sect originally said it wanted sharia, Islamic law, to be applied more widely across Nigeria but its aims appear to have changed. Recent messages from its leaders have said it is attacking anyone who opposes it, at present mainly police, the government and Christian groups.

"Since 2009 it is an insurgency that has gathered pace almost in slow motion, incrementally - apparently absorbed and accommodated with no clear evidence that government has the capacity, competence or will to turn the tide," said Antony Goldman, head of Nigeria-focused PM Consulting.

"Boko Haram was a work in progress when (former President) Obasanjo, who had a deserved 'no nonsense' reputation, was in power; and it was Yar'Adua, a Muslim President, who ordered a bloody crackdown in 2009. It was a difficult inheritance for Jonathan but the problems have only grown more complex."

Boko Haram's attacks have become increasingly deadly in the last few months.

At least 65 people were killed in the northeast Nigerian city of Damaturu, Yobe state, in a spate of gun and bomb attacks in November.

A bomb attack on a Catholic church just outside the capital Abuja on Christmas Day, claimed by Boko Haram, killed 37 people and wounded 57.

In a Reuters interview in late December, National Security Adviser General Owoye Andrew Azazi said officials are considering making contact with moderate members of shadowy sect via "back channels", even though explicit talks are officially ruled out.