The EU-backed tribunal in The Hague, Netherlands, convicted Thaçi of war crimes committed during the war against Serbia, several media outlets report.
The 58-year-old, who has been accused of being behind more than 100 murders of political opponents, stood silently in a suit and tie when the verdict was read out on Wednesday.
Hashim Thaçi is seen by supporters as a hero in Kosovo's fight for independence from Serbia, but prosecutors say his regime used arbitrary detentions, torture and murder of dissidents to consolidate its power after the 1998-1999 war.
Thaçi denies any wrongdoing.
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