Warning: Video contains images that some may find disturbing.

A Norwegian citizen has been named as a suspect in the terror attack on the Westgate shopping centre in Kenya.

Hassan Abdi Dhuhulow, 23, is said to have left his home in the coastal town of Larvik, 75 miles south of Oslo, for Somalia in 2009 and taken part in the attack by the militant group, al-Shabab, on the shopping centre last month, which left 67 dead.

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According the BBC's Newsnight, Dhuhulow is believed to be one of four men from the al-Qa'ida linked, Somalia-based terror group shown in CCTV images of the four-day attack, which were also released today.

In the video obtained by CNN, one man can be seen hiding behind a supermarket kiosk as the gunmen storm the mall. As shoppers run for their lives, a terrorist casually approaches the cowering man and fires a bullet into his body from close-range.

In the next clip the man is seen writhing in agony, before a third scene captures him lying in a pool of his own blood as the gunman returns and fires more shots at him. It is believed the man died as a result of his injuries.

Elsewhere in the CCTV footage, a British family - including a four-year-old boy who famously told one of the terrorists he was “a very bad man” - can be seen being told to leave the supermarket by one of the gunmen.

As the mother - who had already been shot in the thigh by a terrorist - leads her children from the store using a shopping trolley to carry one of her injured offspring, she is seen being followed by a terrified, blood-soaked teenage girl, and finally by one of the gunmen.

The BBC reported that Dhuhulow was born in Somalia, but he and his family moved to Norway as refugees in 1999. Speaking anonymously, one of his relatives said he had been “brainwashed”.

Morten Henriksen, one of the family's former neighbours, has not seen Dhuhulow for years.

“He was pretty extreme, didn't like life in Norway… got into trouble, fights, his father was worried,” Mr Henriksen said of Dhuhulow as a teenager.

Stig Hansen, an expert on security and political Islam based in Norway, told Newsnight said that he was not surprised to learn that a Norwegian citizen was suspected of taking part in the attack.

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He said that an estimated 20-30 Norwegians had gone to Somalia to sign up as fighters for the Islamist militant group al-Shabab. “ The biggest problem is the so-called 'Generation 1.5', those who weren't born in Norway, but came when they were quite young, falling between two cultures,” he said.

Last week, officers from Norway's intelligence agency PST travelled to Kenya in a bid to verify reports that a citizen had been involved in the shopping centre attack on 21 September.

Video: CNN news report on the CCTV footage from Westgate mall