'Al-Shabaab video' calls for attacks on London shopping centres including Oxford Street and Westfield

Extremist group says the 2013 attack on the Westgate Mall in Nairobi was in retaliation for Kenyan military involvement in Somalia

The video threatens an attack on the Mall of America, on the US's largest malls

A video claiming to be by Somalia's al-Qaeda-linked rebels has urged Muslims to attack London shopping sites including Oxford Street and Westfield Stratford City.

A video purporting to originate from an al-Qaeda-linked militant group has called for attacks on shopping centres in London.

In the video, which is being examined by police specialists, the extremist group al-Shabab says it wants its supporters to carry out an attack in the UK similar to the deadly 2013 shooting at the Westgate Mall in the Kenya.

A total of 67 people died in the attack on the Kenyan shopping centre, which lasted over a number of days in September 2013.

Hundreds of newly trained al-Shabab fighters perform military exercises (AP)

The video says that attack, in the country’s capital of Nairobi, was carried out in retaliation for the country’s military involvement in Somalia.

The 76-minute cut features a collage of news footage of the fighting of the previous attack as well as a balaclava-clad man talking to camera.

The narrator of the clip warns of more attacks in the east African country, but also identifies targets in the West.

Westfield Stratford City, one of the purported targets (Getty Images)

Oxford Street and a Westfield shopping centre in London are identified, as well as the vast Mall of America in the US city of Minneapolis and the West Edmonton Mall in the Canadian province of Alberta.

The authenticity of the video could not be verified.

Security has been increased at the North American targets mentioned, the Press Association news agency reports.

London’s Metropolitan Police however said it did not comment on security matters.

A Metropolitan Police spokesperson said: “The MPS Counter Terrorism Command is aware of the video and is assessing the content.

“We remind the public that downloading extremist material may constitute an offence.”

Armed members of the militant group al-Shabab attend a rally on the outskirts of Mogadishu, Somalia in 2012 (AP)

Last week al-Shabab suicide bombers launched a deadly attack on a luxury hotel in Somalia, killing at least 11 people and wounding the anarchic country’s deputy prime minister.

Last November the group reportedly slaughtered 28 non-Muslims on a bus after they failed to recite verses from the Koran.

A few months earlier it claimed responsibility for dozens of killings on the Kenyan coast in a space of brutal attacks.