A suicide bomber hiding explosives in his turban has blown himself up, killing four people, inside a mosque during a memorial service for Afghan president Hamid Karzai's assassinated half brother, Ahmed Wali Karzai.
Officials believe the bomber got the explosives past security by hiding them in his turban.
Among the victims of the attack in Kandahar city was Hekmatullah Hekmat, head of the clerical council for the province, and a young child. At least 15 people were wounded, including an MP.
Kandahar governor Tooryalai Wesa, who was at the memorial, said he saw the man's turban explode. The bomber approached Hekmat after mourners ended a prayer, the governor said.
No one immediately claimed responsibility for the attack.
The Sarra Jamai mosque in the southwest of the city had been filled with relatives and friends of Ahmed Wali Karzai.
"There was a prayer going on and after that prayer the man came close to the director of the religious council and exploded," Wesa said. "It looks like he was targeting the director."
Wali Karzai was shot at close range by a bodyguard, leaving President Karzai without a powerful ally in Kandahar, a former Taliban stronghold and the site of recent military offensives by the US-led military coalition.
The Taliban claimed responsibility for the killing, which has threatened to create a power vacuum in the south.
Wali Karzai was regarded as the most powerful man in southern Afghanistan. He was head of the provincial council, the influential Populzai tribe, and the Afghan president's confidant.
The mosque bombing was the second attack in Kandahar city yesterday. In the morning a bomb exploded near a police vehicle killing one civilian, said provincial police chief Abdul Raziq.
As the conflict in southern Afghanistan intensifies, the UN has said that civilian deaths jumped 15% in the first half of 2011. The UN blamed a rise in insurgent roadside bombings and suicide attacks for the increase.
The UN said 1,462 Afghan civilians were killed. In the first half of last year, 1,271 civilians died.
Yesterday officials in eastern Afghanistan accused Nato troops of killing six civilians in an overnight raid, and more than 1,000 people poured onto the streets of Khost in anger.
The military alliance said the joint patrol in Khost killed six militant fighters.
Wali Karzai, who was in his 50s and had survived several previous assassination attempts, was seen by many as a political liability for the Karzai government after a series of allegations, including that he was on the CIA payroll and involved in drug trafficking. He denied the charges. Wali Karzai remained a key power broker in southern Afghanistan, helping shore up his family's interests in the Taliban's southern heartland, which has been the site of numerous offensives by US, coalition and Afghan troops in attempts to root out insurgents. Militants have retaliated by intimidating and killing local government officials or others against the Taliban.