Suicide Bombing at Kandahar Dogfight (AP)
Kandahar provincial Governor Assadullah Khalid put the death toll at 80, while another government official said the number wounded was around 50.
The target of the attack, which happened on open ground on the outskirts of the city, is alleged to have been militia leader Abdul Hakim Jan, according to provincial council president Wali Karzai in comments reported by The Associated Press.
Wire reports say Hakim Jan, an ex-police chief of the province who in the past opposed the Taliban, died in the blast.
There were reports of shots fired by bodyguards after the attack, the agency added, raising the possibility that some of the casualties may have been caused in the crossfire.
Interior Ministry Spokesman Zamary Bashary called the blast a "very bad" suicide attack.
"The police are investigating the case," Bashary. "Right now we are sure it was a suicide bomber. Some parts of the legs are remaining on the spot."
Speaking to VOA, he condemned what he called the "criminals" behind the attack and said it shows the perpetrators are opposed to the Afghan people.
More than 500 people had gathered for the dog-fighting competition, said Abdul Karim, who had been in the crowd to take part in the popular winter pastime, which was banned from 1996 to 2001 under the Taliban government.