Richard Dawkins has caused uproar by questioning the motives of Ahmed Mohamed, the 14-year-old who was arrested after his teacher thought a clock he made was a bomb.

Dawkins queried the boy's motives on Twitter, agreeing that he should not have been arrested but asking whether the boy had truly invented the clock, as had previously been reported.

He has also criticised the tech firms who have sent Mohamed freebies and potential job offers in response to his clock invention.

Mohamed was arrested at MacArthur high school in Irvine Texas last Monday and suspended for three days for bringing in what his teacher thought was a hoax bomb.

He was not allowed to call his parents, he told MSNBC.

"I felt like I was a criminal, I felt like I was a terrorist. I felt like all the names I was called.

"In middle school I was called a terrorist, called a bomb maker, just because of my race."

His arrest prompted accusations of racism and Islamophobia against Mohamed, whose parents are from Sudan who is now transferring to another school.

He was shown huge support on Twitter by Silicon Valley tech companies and was invited to the White House by President Obama in response to the mistaken arrest.

Richard Dawkins, a scientist and critic of religion, was sceptical of Mohamed's intentions.

"He disassembled & reassembled a clock (which is fine) & then claimed it was his "invention" (which is fraud)," Dawkins wrote on Twitter.

He linked to a YouTube video entitled "Mohammed [sic] Clock is a FRAUD," in which it alleges the clock "is in fact not an invention. The 'clock' is a commercial bedside alarm clock removed from its casing."

In reaction to the video, Dawkins said, "If this is true, what was his motive? Whether or not he wanted the police to arrest him, they shouldn't have done so."

He tweeted again in support of the video: "This man seems to know what he's talking about."

"If the reassembled components did something more than the original clock, that's creative. If not, it looks like hoax," he said.

Dawkins later retreated from his harsh postion towards Mohamed, redirecting his criticisms away from the child towards the police motives.

He apologised saying, "Sorry if I go a bit over the top in my passion for truth."

He later retweeted President's Obama's White House invitation to the boy.

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