A suicide bomb exploded in crowds at a traditional horse-back game of buzkashi in northern Afghanistan on Wednesday, killing at least six people, police said. "The suicide attacker detonated himself at the end of the match in Imam Sahib district this evening. Six people have died," Abdul Khalil Andarabi, police chief of Kunduz province, told AFP. Buzkashi is Afghanistan's national sport in which riders use a headless goat in place of a ball in a ferocious version of polo.