They say so - if you beleive youtube source:
In 1989 during a TKD competition in Vigo (Spain) a Brazilian fighter kicked a competitor from Marocco in the head. The fighter from Marocco died 3 days later in a local hospital. There was no criminal charges. It was considered a unfortunate accident.
and another in Poland:
Death in Taekwondo (but looks like kickbox) competition in December 2005, in Poland, Lodz. 22-years old fighter died from neck injury. It was light contact fight.