Islamist terror group singles out specific British Muslims in video that incites people to 'cut the necks of the disbelievers'

A prominent British Muslim commentator is being protected by police following concerns over his safety following the release of a video by Somali-based terror group, al-Shabaab, which singled out several British Muslims for having criticised jihadists in the aftermath of the Woolwich murder.

Mohammed Ansar, a filmmaker and journalist who has spoken out against extremism in Islam and the far right, said police visited his home at midnight on Wednesday, concerned for his safety after Shabaab released an hour-long film, The Woolwich Attack: It's an Eye for an Eye.

Other British Muslims named in the film have also been contacted by police and offered security advice since the video's release, the Guardian has learned.

Narrated by a man with a British accent, wearing a black mask and a camouflage jacket, the Shabaab production praises those behind the murder of Drummer Lee Rigby, describes the Woolwich killings as "a new and terrifying reality" and incites others to carry out attacks in the UK.

In the film, the jihadist group, which has also claimed responsibility for the bloody Kenyan Westgate mall attack, singles out specific British Muslims, including Ansar, who have distanced "themselves from the mujahideen who carried out these attacks" as having "mutilated the teachings of Islam".

Holding an automatic weapon in his hands, the narrator tells people to purchase knives: "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."

At the end, the narrator encourages others to follow the example of the Woolwich killers and not to let the security services put them off.

Released to coincide with the Muslim festival of Eid al-Adha, which ended on Tuesday, the film also identifies 11 British "martyrs" who have died fighting for al-Shabaab.

One British man, named as Talha from Tower Hamlets in east London is shown calling on others to follow him: "I call upon you today all the Muslim men in Britain, especially the people of Tower Hamlets who are in the city I was born in … I call upon you to come to jihad, and raise the banner, humiliate the disbelievers, cut the necks of the disbelievers."

The video appears to have been made before the attack on the Westgate shopping centre in Nairobi, Kenya, as there is only one brief mention of the "suffering of Muslims in Kenya."

Ansar, 39, who has four young children living with him at his home said police were now regularly patrolling his residence and were making contact by phone every hour.

The journalist, who has features in a documentary about the former EDL leader Tommy Robinson that will air later this month on BBC1, became a prominent figure after condemning Rigby's murder the day after his death but says he has never been the subject of an explicit threat before.

Ansar said he was alerted to the video before a plain clothes inspector and a uniformed officer arrived at his home in the small hours. "If they [jihadists] are going to start targeting British Muslims and set fanatical extremists against them then that is a frightening new dimension," he said.

Usama Hasan, a senior researcher with the anti-extremist Quilliam Foundation, was another of those that featured in the video. He said he had seen the film on Wednesday when it was released and was not surprised when police turned up at his home at 9.30pm, warning him he could be in danger. "The video is idiotic but also chilling in many ways. This guy has a British accent and he is using the language of fascism about the deaths of kuffar [non-believers]."

The imam and broadcaster Ajmal Masroor said the authorities had also made contact with him after he was also named in the film. "Extremism in all its forms is nasty and has a self destructive property … the truth is moderation will always prevail," he said.

Scotland Yard said: "We are aware of the video and we are assessing its contents and looking into it."

• This article was amended on 18 Ocrtober 2013. An earlier version said Mohammed Ansar had made a documentary about the former EDL leader Tommy Robinson that will air later this month on BBC2. He features in the documentary, which will be shown on BBC1.