There were no officers in sight at the ransacked and partially burnt police station attacked the night before -- only neighbourhood boys trying to control the crowd gathered to see the damage.

"Some of them came along this street with a car and some motorcycles," a resident trying to keep youths out of the station said of Tuesday night's attackers in Kano, Nigeria's second-largest city.

"Another group came from another route with a Mercedes and motorcycles."

It was yet another sign of the Nigerian authorities' inability to stop an onslaught of attacks blamed on Islamist group Boko Haram that have deeply shaken Africa's most populous nation and largest oil producer.

The worst yet came on January 20, when attackers, including five suicide bombers, descended on various neighbourhoods in Kano, setting off explosions and gunning people down with AK-47s.

Security forces were the main targets, with a number of police stations as well as state police headquarters hit in the attacks.

At least 185 people were killed in the coordinated attacks, which marked a new escalation in the violence blamed on Boko Haram, with Kano the commercial heart of Nigeria's mainly Muslim north and a centre of Islamic culture.

Tuesday night's bomb and gun attack on a police station was far less violent -- police reported three wounded -- but the fact that it happened only days after Friday's siege raised further questions over the government's response.

Some point to a badly corrupt police force as a major part of the problem.

"People are more concerned with getting money for themselves than doing the job for which they are engaged," said Abubakar Tsav, a respected former police chief for the economic capital Lagos who now lives in Kano.

After sticking to mostly vague statements in public despite the enormity of the bloodshed, Nigerian President Goodluck Jonathan moved Wednesday to drastically overhaul the police force.

He fired police chief Hafiz Ringim and all Ringim's deputies, replacing him with veteran cop Mohammed Abubakar.

The new chief faces a mountain of troubles. Some have even evoked the possibility of civil war in Nigeria, roughly divided between a mainly Muslim north and predominately Christian south.

Jonathan has labeled the attackers "terrorists," but offered little more explanation. He has pledged that the government will pursue the backers of "so-called Boko Haram," without indicating their motives.

He has also said Boko Haram sympathisers have infiltrated the government and security forces, but has not said how -- or why they have not been arrested.

"There have been serious criminal justice failings in the Nigerian government’s response to Boko Haram," rights group Amnesty Inernational said this week.

There are multitudes of theories on what Boko Haram is and who is behind it. What seems clear is, whoever they are, they appear able to attack at will.

Some have been eager to argue that the group has ties to Al-Qaeda's north African branch or other extremists, while others say Boko Haram is a problem born and bred in Nigeria.

They point to the massed ranks of unemployed youths with little hope for the future in a country where corrupt elites have siphoned off oil wealth while most of the population lives on less than $2 per day.

They cite the disappointing loss of power for Nigeria's north, which had been slated to hold the presidency for two terms under a loose power-sharing agreement in the ruling Peoples Democratic Party.

Umaru Yar'Adua, a northern Muslim, died before finishing his first term and was replaced by then vice president Jonathan, a southern Christian who defied many elites in the north to run in April 2011 elections.

In seeking to put Boko Haram in context, some point to violence that rocked the oil-producing Niger Delta region for years before a 2009 amnesty.

That conflict involved a complex mix of militants, profiteers, political gangs and others, often fighting under the banner of militant group MEND.

But while the comparison offers some insight, the Niger Delta conflict did not involve suicide bombers and brutal attacks targeting civilians.

It did not take on a sectarian tone in the way attacks on churches blamed on Boko Haram have. In the end, delta militant leaders agreed to an amnesty.

"MEND has always been about money," former US ambassador to Nigeria John Campbell wrote this week.

"Accordingly, the government was able to buy the group’s various warlords when the price was right ... Boko Haram is more focused on political power."

Boko Haram has no clear structure and is thought to have a number of factions, including a hard-core Islamist wing and others with political links.

The group, which initially said it was fighting for the creation of an Islamic state in deeply impoverished northern Nigeria, launched an uprising in 2009 put down by a brutal military assault.

It went dormant for more than a year before re-emerging with attacks that have become increasingly sophisticated.

"Everybody is confused," a prominent Kano resident who lives in one of the neighbourhoods hard-hit in the attacks said. "Their motive is to kill people."