A man hiding explosives in his turban blew himself up inside a mosque where Afghan officials were attending a memorial service for the president's assassinated half brother, killing five people.
The attack in Kandahar city heightens fears that security in the already volatile south will unravel with the death of Ahmed Wali Karzai, who was considered the region's most powerful man.
The Sarra Jamai mosque had been filled with relatives and friends of Wali Karzai, two days after he was shot at close range by a confidant at his home. President Hamid Karzai was not at the memorial service, having returned to Kabul after his brother's funeral on Wednesday.
President Karzai said the bombing inside a mosque was an attack on religious faith.
The attacker appeared to have targeted Hekmatullah Hekmat, the head of the provincial clerical council, who was among the dead, according to Kandahar Gov. Tooryalai Wesa.
"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."
The Kandahar provincial government said all other high-ranking officials who had been at the ceremony were safe and had been taken to a secure location.
No one immediately claimed responsibility for the attack, which also killed a child and wounded 15 people, the Interior Ministry said.
Officials believe the bomber got the explosives past security by hiding them in his turban.
The governor, who was attending the memorial, said he saw the man's turban explode. Provincial intelligence chief Gen. Mohammad Naeem Momin said authorities drew the came conclusion after examining the bomber's remains.
Tuesday's slaying of Wali Karzai left the president without a powerful ally and threatened to create a power vacuum in the former Taliban stronghold and the site of recent military offensives by the US-led military coalition.
Wali Karzai was head of the Kandahar provincial council, the influential Popalzai tribe, and the Afghan president's confidant and emissary. But beyond his more official roles, Wali Karzai was also known as a master operator who played Kandahar's hard-line tribal and political factions against one another to retain ultimate control over the restive province.
"Now that he's not here, the insurgents are going to show their power more openly than before," said Nayamatullah Sherbalai, a provincial council member. Sherbalai said Wali Karzai kept feuding tribes and political factions united against the Taliban.
"He didn't allow those divisions. People were working together," Sherbalai said.
Even the international alliance begrudgingly accepted Wali Karzai's sweeping influence in southern Afghanistan, despite their strong suspicions that he was involved in opium trafficking, smuggling and other criminal enterprises.
The mosque bombing was the second attack in Kandahar city Thursday. A bomb exploded hours earlier near a police vehicle in the city, killing one civilian, provincial police Chief Abdul Raziq said.
The United Nations said Thursday that civilian deaths jumped 15 percent in the first half of 2011 as the conflict intensified in the south and southeast of Afghanistan. The UN blamed a rise in insurgent roadside bombings and suicide attacks.
The UN said 1,462 Afghan civilians lost their lives — many in the crossfire of battles between Taliban insurgents and Afghan, US and Nato forces. During the first half of last year, 1,271 Afghan civilians were killed.
But many of the most contentious incidents continue to be international military strikes in which residents routinely report that civilians are killed.
In the latest such dispute, government officials in eastern Afghanistan accused Nato troops of killing six civilians in an overnight raid. More than 1,000 people poured into the streets of Khost province in anger, chanting "Death to America! Death to the government" and carrying the bodies of the dead on their shoulders.
The military alliance said the joint patrol with Afghan forces in Khost province killed six fighters from a militant group allied with the Taliban known as the Haqqani network and injured one civilian.
"I don't have any indication that we killed civilians," Capt. Justin Brockhoff told The Associated Press.
The raid took place in the village of Toora Worai about four miles (seven kilometers) from the provincial capital of Khost city. Provincial government spokesman Mubarez Zadran said the international forces were acting on a false report that a group of Haqqani leaders were meeting in the village.
Brockhoff said that Nato and Afghan forces were going after a Haqqani leader who was responsible for attacks and weapons trafficking in the area. He said all of those killed were firing on the troops, including a woman who was armed with a pistol.
President Karzai ordered an investigation into the incident.