London, UK - Prominent British Muslims who have spoken out against Islamic extremism say they will not be cowed despite being targeted by al-Shabab in a broadcast calling for do-it-yourself attacks by self-styled jihadists in the UK.

The video, which appeared on the internet last week and bore the watermark of the Somali armed group's al-Kataib media wing, is presented by a black-masked narrator with a southern English accent who urges aspiring jihadists to arm themselves with knives from B&Q, a popular DIY or "do it yourself" store famous for the slogan "Don't just do it, B&Q it".

It celebrates the murder of British soldier Lee Rigby in Woolwich, south London, in May, and accuses Muslim community leaders who condemned the attack of being on the British government's payroll and of "mutilating the teachings of Islam".

It didn't make me scared. It just made me angry and more determined -Ajmal Masroor, imam

Ajmal Masroor, a London-based imam and broadcaster, said police officers had visited his home late last Wednesday to warn him of a credible threat against his life made in an online video.

"It is a terrible piece of work and the content is vile and disgusting and horrific in many ways. It is a group of people who are glorifying violence and death. It didn't make me scared. It just made me angry and more determined," Masroor told Al Jazeera.

Mohammed Shafiq, chief executive of the Ramadan Foundation, which works to enhance understanding between Muslims and non-Muslims, said he had also received a visit from police in the early hours.

Shafiq told Al Jazeera he was concerned for the safety of his family, and said police had offered him protection at his Manchester home.

"It's shocked us all but it just makes you even more determined to make a stand against terrorism," he said. "Not because of what the government says, but because it is our Islamic duty to stand up against this. We must confront it wherever we find it."

Other figures targeted in the video included Mohammed Ansar, a filmmaker and broadcaster who regularly challenges both Islamic and far-right extremism, and Usama Hasan, senior researcher at the Quilliam Foundation, a counter-extremism think-tank.

Ansar said police were patrolling his neighbourhood and had installed alarm systems and reinforced locks and doors at his home. Summing up his response to the ordeal on Twitter he wrote: "Typical British responses if ever we saw them. Defiance and cups of tea."

The video also lists fighters from several British cities killed on the battlefields of Somalia and features footage of an al-Shabab member identified as Talha from Tower Hamlets, a London borough, calling on "all the Muslim men in Britain to come to jihad... and cut the necks of the disbelievers."

Domestic 'terrorism'

But it also urges would-be jihadists in the West to consider taking action closer to home, citing the examples of Woolwich, the Boston marathon bombings in April, last year's Toulouse killings in France and the Fort Hood shootings in Texas in 2009.

For them now to openly suggest to Muslims living in other parts of the world to take up weapons and knives from B&Q... it's too vague. Somebody is going to do the wrong thing and that is not going to be of benefit to the jihad or to Muslims. -Al-Shabab activst

"Just follow the examples of your brothers in Woolwich, Toulouse, Texas and Boston," the narrator says, brandishing an automatic weapon. "Do not waste your time trying to reinvent the wheel. If you can't afford to get hold of one of these then certainly a simple knife from your local B&Q will do the job."

A British-based activist sympathetic to al-Shabab's cause in Somalia said the group, which is a banned terrorist organisation in the UK, had long been a popular destination for British fighters.

"Al-Shabab have shown they are a professional force and they don't mind foreign fighters, so it has become an open ticket for foreign Muslims to go and fight there. What they are doing in Somalia is legitimate according to Sharia and they have every right to protect their territory."

But the activist, who did not want to be named, said al-Shabab was making a mistake in trying to incite attacks on British soil.

"For them now to openly suggest to Muslims living in other parts of the world to take up weapons and knives from B&Q... it's too vague. Somebody is going to do the wrong thing and that is not going to be of benefit to the jihad or to Muslims. This is something they need to revisit and look at from a different perspective."

Analysts said the video appeared to confirm a shift in al-Shabab's strategy signalled by last month's Westgate shopping mall attack in Nairobi away from the group's traditional goal of establishing Sharia law in Somalia towards carrying out and inspiring al-Qaeda-style global operations.

'A call to arms'

Ahmed Soliman, a Somalia expert at the Chatham House think-tank, said Ahmed Abdi Godane, the current al-Shabab leader who pledged allegiance to al-Qaeda last year, seemed to have won out over factions wary of broadening the struggle beyond Somalia's borders.

"Internally there seems to have been quite a bit of upheaval but what we are seeing now is confirmation that it is this global jihadist arm that is taking over and dominating. This is a call to arms, a rallying cry, almost a promotional video," Soliman told Al Jazeera.

Soliman said the UK was an obvious target for the group because of the presence of a sizeable Somali population and because the government had hosted two high-profile conferences on Somalia which had helped the current transitional government to establish its international credibility.

Valentina Soria, an analyst at IHS Jane's Terrorism and Insurgency Centre, said the video, following so soon after the high-profile Westgate attack, appeared part of a concerted campaign to recruit fresh fighters from western countries at a time when al-Shabab was losing ground domestically and Somalia's appeal as a destination for "jihad tourism" had been dented by the lure of the war in Syria.

"This has boosted their profile in jihadist circles and that is quite important because the likes of al-Shabab have suffered from the Syrian conflict and the fact that every jihadist wanted to go to Syria to fight," she told Al Jazeera.

Soria said the Westgate attack and regular bombings inside Somalia highlighted the threat that al-Shabab continued to pose in East Africa even as they have suffered strategic defeats on the ground against combinations of Somali government, African Union, Kenyan and Ethiopian forces.

But she said the video also hinted at the group's more limited abilities to take the fight to Western countries. "If anything, it is evidence of an inability to carry out more sophisticated attacks on their own, so they have to rely on the likes of single extremists."

For now though, British Muslims targeted by the group are taking the threat very seriously.

Ajmal Masroor said he had received unanimous support after addressing the threat in his Friday sermon at a central London mosque.

"People were saying, 'How dare they?', and even volunteering to be my bodyguard. So there is a spirit in the community to fight back. I think it is about time we did more fighting back."

Or, as Mohammed Ansar put it on Twitter: "A little odd when an act of defiance is popping down to the Cafe Nero [sic] with Mrs A for a coffee and a toasted panini."

Follow Simon Hooper on Twitter: @simonbhooper