Elon Musk has bought US$25 million ($35.6m) worth of stock in Tesla, as the electric car company announced it was slashing 9 per cent of jobs due to "duplication of roles".

The move, seen by many as a strategic manoeuvre by Musk to show his optimism over Tesla's future, prompted shares to push higher in after-hours trading.

The chief executive bought around 72,000 shares, taking his holding in the business to 34 million, or around a 20 per cent stake, according to the Daily Telegraph.

News of the share purchases, which took place on Tuesday and Wednesday, comes just one day after Tesla said it would be cutting around 3,000 roles, in what Musk said had been a "difficult decision".

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"Given that Tesla has never made an annual profit in the almost 15 years since we have existed, profit is obviously not what motivates us," he wrote in an email to employees and later posted on Twitter.

This is not the first time that Musk has responded to developments in the company with share purchases, having in May bought around US$10m in shares after criticising those shorting the stock.

Writing on Twitter he said: "Oh and uh short burn of the century comin soon. Flamethrowers should arrive just in time."

He also cut off two analysts during a tense earnings call at the start of May, saying "boring bonehead questions are not cool", later claiming he had done so because they were short sellers.

The value of Musk's stake after the buys is around US$11.7 billion and his net worth is around US$20.1b.