Jo Cox's alleged killer was a 'dedicated supporter' of an American Neo-Nazi group

The alleged killer of British Labour MP Jo Cox, who died of gunshot and stab injuries on Thursday afternoon, was a "dedicated supporter" of the National Alliance (NA) - a neo-Nazi organisation in the US, according to the think tank Southern Poverty Law Center (SPL Center).

The group says Thomas Mair, who was arrested at the scene of the crime in Cox's West Yorkshire constituency Batley and Spen, purchased a manual from the NA in 1999, which included instructions on how to build a pistol. Mair reportedly used a homemade pistol to carry out the attack. Those reports have not been confirmed by the police.

The SPL Center adds that invoices show that Mair sent $620 (£435) to the NA for subscriptions to periodicals, including works titled "Chemistry of Powder & Explosives," "Incendiaries," and "Improvised Munitions Handbook." There are also receipts for "Ich Kampfe," an illustrated handbook issued to members of the German Nazi party in 1942.

Two witnesses said Mair shouted "Britain First" before allegedly carrying out the attack, but police have not confirmed those reports.

The NA was founded in 1970 and produced, according to the SPL Center, a number of activists who later became "assassins, bombers and bank robbers."

Its founder William Pierce died in 2002 and the group split up and subsequently lost most of its members. Pierce was the author of the novel "The Turner Diaries," a white supremacist fantasy that became the inspiration for Timothy McVeigh's 1995 bombing of the federal building in Oklahoma City, which killed 168 people, and many other acts of terror.

Quotes from the NA's website include: "[O]ur responsibility now is to continue building a revolutionary infrastructure able to support an opposing power structure which can respond advantageously to all developments," and "We must have new societies throughout the White world which are based on Aryan values and are compatible with the Aryan nature."

The news of Mair's link to the NA follows the discovery by the Daily Telegraph that he also subscribed to a South African pro-apartheid magazine called "S.A. Patriot." The magazine's editorial stance says it opposes multicultural societies.

Jo Cox, who had been an MP for less than a year, was a staunch proponent of the UK remaining in the EU in the June 23 referendum. Brexit campaigning from sides has been called off today as a mark of respect.