Michael Salonen, 43, was arrested in Thailand in April last year, and claims he is innocent of the crimes.
But the court found that in 2017, he sent an envelope containing a white powder and threats to 21 members of the Swedish government, including Prime Minister Stefan Löfven, and to local officials and cultural personalities.
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The powder turned out to be harmless, but Salonen's actions were aimed at “spreading fear” and “putting society under pressure”, the Stockholm appeals court said in its ruling.
It increased the district court's sentence from seven to eight years in jail.
In the summer of 2017, Salonen had sent a booby-trapped letter to a bitcoin sales company in London. The letter did not explode when it was opened, but was “intended to kill or cause serious bodily harm”, the court said, upholding Salonen's conviction for attempted murder.
Swedish politicians claim to have increasingly been the target of threats and insults on social media.
In September 2003, Foreign Minister Anna Lindh, travelling without an escort, was stabbed to death in a Stockholm department store by a 24-year-old Serbian-born Swede with a history of psychiatric problems.
Prime Minister Olof Palme was shot dead in Stockholm in 1986 when he was walking from the cinema with his wife, having decided to go without his security guards.