A suicide bomber hiding explosives in his turban assassinated the mayor of Kandahar on Wednesday, just two weeks after President Hamid Karzai's powerful half-brother was slain in the southern province that is critical to the U.S.-led war effort.

Mayor Ghulam Haider Hamidi, 65, was the third powerbroker from southern Afghanistan to be killed in just over two weeks, underlining fears of a surge in violence in the wake of the slaying of the president's half brother.

The grey-haired mayor was slain inside a heavily fortified government compound just before he was to meet with local residents caught up in a land dispute, according to Mohammad Nabi, an employee of the mayor's office. The attacker was holding a piece of paper and trying to talk to the mayor when he detonated a bomb hidden inside his turban, said Nabi, who witnessed the killing.

"After that, there was some shooting," he said. "I hid behind a wall. The windows were shattered. There was dark smoke."

In the aftermath, part of the attacker's black and gray-striped turban was strewn on the ground next to a blood-spattered tree.

One civilian was also killed and another civilian and a security guard were wounded, the governor's office said.

Hamidi was buried Wednesday evening in a family plot near Kandahar University. Karzai's elder brother, Qayyum Karzai, was overcome with grief at the funeral.

"It is a bad day for Kandahar and it is a bad day for Afghanistan. The Kandahar mayor was an honest Muslim who was serving the country," Qayyum Karzai said, then wiped tears from his eyes with both hands and walked away.

The Taliban have claimed responsibility for all three attacks, yet the area is rife with tribal rivalries and criminals and it is not yet certain who is behind the trio of killings.

Ahmed Wali Karzai was gunned down in his home in Kandahar by a close associate on July 12, leaving a power vacuum in Kandahar and dealing a blow to the strength of the president's support as well as the stability of the south where the Taliban hold the most sway.

Five days later, Karzai's inner circle suffered another hit when gunmen killed Jan Mohammad Khan, an adviser to the president on tribal issues and a former governor of Uruzgan province, also in southern Afghanistan. A member of parliament also was killed in the July 17 attack at Khan's home in Kabul.

Taliban spokesman Qari Yousef Ahmadi told The Associated Press that they killed the Kandahar mayor because he had ordered the destruction of homes that city officials claimed had been illegally constructed. Ahmadi said the mayor was killed to avenge the deaths of two children who were killed during the demolition work.

Kandahar Gov. Tooryalai Wesa said the two children were accidentally killed by a bulldozer knocking down the homes.

Late mayor had family in Canada

Hamidi, who has family in Toronto, spent 30 years in exile in Arlington, Va., as an accountant before being appointed mayor of the volatile provincial capital by Hamid Karzai in 2007.

During his time as mayor, Hamidi became the enemy of the Taliban as well as others involved in criminal activities.

The mayor's son-in-law, Abdullah Khan, said Hamidi had launched a campaign against warlords and criminals and was particularly harsh on people who took illegal control of property. Just two days before the killing, he said his father-in-law had ordered several large homes torn down because they had been built illegally.

"I don't know who did this," Khan told the AP in a telephone interview. "From day one I was afraid. Even I wanted to put pressure on him to leave.

"It is up to the police to investigate, but we don't really have police that can do a good investigation," Khan said.

Ryan Crocker, the new U.S. ambassador to Afghanistan, and Gen. John Allen, the new commander of U.S. and NATO forces in Afghanistan, both condemned the assassination.

Crocker told reporters during his first briefing at the U.S. Embassy in Kabul that the assassination was indicative of the challenges ahead in Afghanistan.

"Assassinations are horrific acts — they are acts of terror and can have major impacts," he said. "But I don't think you can chart a straight line that says that three assassinations guarantees a total unraveling either of international support or Afghan confidence. It could very well go the other way."

Fears security is falling apart

Militants have targeted scores of government officials in Kandahar, heightening fears that security in the already volatile south is unravelling.

In April, a suicide bomber wearing a police uniform killed Khan Mohammad Mujahid, the Kandahar provincial police chief and one of the most prominent law enforcement officials in the nation. Two deputy mayors also have been killed — one in April 2010 as he knelt for evening prayers in a mosque and another during an insurgent attack in October 2010.

Two days after the president's half-brother was slain, a suicide attacker, also with explosives hidden in his turban, blew himself up inside a mosque where Afghan officials were attending a memorial service for him.

Hamidi was considered to be Wali Karzai's ally in Kandahar. But Hamidi operated behind the scenes and his tribal contacts were not considered strong, leading some to speculate that he could not take over for Wali Karzai, a master operator who played Kandahar's hard-line tribal and political factions against one another to retain ultimate control over the restive province.

According to the Kandahar governor's office, Karzai had offered Hamidi other posts, but that he had chosen to remain mayor. Karzai had offered to appoint Hamidi as a deputy finance minister, the head of the government's local governance unit in Kabul as well as the governor positions in Herat and Kandahar provinces.

"He was struggling with all the powerful people in Kandahar, the land grabbers and people who were breaking the law," the governor's office said in a statement. "That's why the militants targeted him."

Hamidi, who was from Kandahar's Arghandab district, attended high school in Kandahar and Kabul University. He worked for 13 years in the Afghan Finance Ministry's budget department and was employed at a government bank. He moved to Pakistan and later to the United States and then returned after the collapse of the Taliban regime in 2001.

With files from The Canadian Press