Are Nigeria's Boko Haram getting foreign backing?

At least six people were killed when the police HQ was bombed

Last week's bomb attack by Boko Haram in the capital Abuja has raised questions about Nigeria's ability to defend itself.

But a reassessment is also being made of the nature of the enemy they are confronting.

Having long regarded the Islamist sect as a localised problem, security sources have told the BBC that they now believe the radical Islamist group to be receiving training and expertise from outside Nigeria.

Boko Haram have, until recently, focused their activities in the far north-east of the country and as you approach the city of Maiduguri there are checkpoints at regular intervals.

At each a security officer, clad in bulletproof black and clutching a machine-gun peers into your vehicle.

This is part of "Operation Flush", the Nigerian authorities' attempt to clamp down on the Islamist sect.

So far there has been little sign that it works.

In the last few weeks Boko Haram appear to be bombing police stations at will.

No longer are the attacks confined to the north-eastern state of Borno either.

Last Thursday in their most high-profile strike yet, they detonated a vehicle in the parking lot of national police headquarters in Abuja.

Trained in Somalia?

Nigeria's President Goodluck Jonathan urged people not to panic but questions are starting to be asked about Boko Haram's recent upsurge in activity.

The police are Boko Haram's main target but they have also bombed churches and assassinated Islamic clerics.

Rev David Bridley says St Patrick's Cathedral was targeted because of its focus on education

St Patrick's Cathedral is Maiduguri's largest with close to 1,000 people regularly packing its pews.

But many of the congregation are making plans to leave.

The compound has just been bombed for the second time in two weeks, with five people dying in the street outside.

"My guess is that because the church is behind education - behind enlightening people we are being targeted," Reverend David Bridley tells me.

"Boko Haram is, I would say, an expression of the al-Qaeda movement and the attack on Christianity. So here, we are the ones taking the heat."

Several Islamic clerics who dared criticise Boko Haram have been assassinated. The only cleric willing to speak to me would only do so on condition that we not film his face or use his voice.

Security sources told the BBC that they believe Boko Haram fighters are travelling to Somalia for training, with some thought to have gone to Afghanistan too.

That information has been been partially corroborated by statements claiming to be from Boko Haram, and unconfirmed reports that Somalis have been detained in Nigeria.

If the links are confirmed, it is worrying news for the authorities who still talk as if the problems is about to resolved.

"In the next couple of weeks and months Boko Haram will become a thing of the past," says Borno state Governor Kashim Shettima.

"Those who are willing to talk to us - the government is willing to enter into dialogue with them. But you cannot negotiate from a position of weakness, you have to negotiate from a position of strength."

And that is why more armoured personnel carriers and troops are pouring into Borno state.

President Jonathan's much vaunted "carrot and stick" solution is seemingly getting ever lighter in the vegetable department.

It is hardly surprising that Boko Haram has shown little interest in the two "carrots" on offer - dialogue and amnesty.

Memories are still fresh of how its leader Mohammed Yusuf was captured alive two years ago - and then shot dead by security forces.

The increased military presence will not help the authorities with their biggest obstacle, the lack of co-operation from the local population. Boko Haram members live among the community but people are either too scared or unwilling to inform on them.

Islamic government

In the back room of a mobile phone shop Abubakar tells me that as he is not a target for Boko Haram, he just tries to steer clear of them.

"The only thing people are scared of is being in an area when they attack - like for example the security forces so we try and stay further away from there."

The police have banned motorbikes at night after a spate of ride-by shootings

Harassment from checkpoints or as some residents call them "toll booths" has helped alienate the police from the Maiduguri population.

"I'm not scared of Boko Haram," Zakaria tells me.

"I am scared of security; whenever they come they bully us all the time."

Like many in town, Zakaria leaves work early to avoid going through checkpoints in the dark.

Despite the increased frequency of their attacks, Boko Haram's message is being blurred by the emergence of more than one people who claim to speak for them.

One spokesman, Abu Abdurahman, told me their aims now go far beyond their initial gripes with Western education.

"We are demanding an Islamic government be established in the northern states. Not this kind of democratic government," he said.

"There is not real Sharia in northern states."

Pressed on foreign support, he said they were inspired by al-Qaeda and the Taliban but that they could not say where they were training for security reasons.

Financial support, he said, was coming from "brothers inside Nigeria".