At least 42 people were wounded.
The attack — which came on the heels of a major upsurge in rebel violence in recent months including assassinations, almost daily clashes with rebels and the kidnapping of an Italian aid worker — further raised fears that militants here are copying the tactics of insurgents in Iraq.
The rebels themselves have suffered a heavy price — losing about 200 men according to American and Afghan officials — but the drumbeat of attacks has belied U.S. claims that it is stabilizing the country, nearly four years after driving the Taliban from power.
Kandahar Gov. Gul Agha Sherzai said the suicide bomber's body had been found, and that he was part of Osama bin Laden's terror network.
"The attacker was a member of al Qaeda. We have found documents on his body that show he was an Arab," Sherzai told reporters.
A purported Taliban spokesman, Mullah Latif Hakimi, said in a telephone call earlier to The Associated Press that the rebels were not responsible for the bombing. Hakimi often calls news organizations, usually to claim responsibility for attacks on behalf of the Taliban. His information has sometimes proven untrue or exaggerated, and his exact tie to the rebel leadership is not clear.
Hundreds of mourners were crowded inside the Mullah Abdul Fayaz Mosque in the center of the main southern city of Kandahar when the bomb went off around 9 a.m., leaving blood and body parts littered over a wide area.
Interior Ministry spokesman Latfullah Mashal said the capital's police commander, Gen. Akram Khakrezwal, was killed along with some other police officers attending the funeral. Mashal said it was a suicide bombing.
Witnesses described the carnage:
"I was knocked unconscious by the blast. When I woke up, so many people were killed or wounded. People were running around, some were lying on the ground crying. Dead bodies were everywhere," said Nanai Agha, a mourner who was inside the mosque but survived the blast because he was behind a wall when the bomb detonated.
Kandahar's deputy police chief, Gen. Salim Khan, said the explosion occurred near where people remove their shoes before praying.