KANDAHAR, Afghanistan — An insurgent suicide bomber hiding explosives in his turban assassinated the mayor of Kandahar on Wednesday, the third killing of a high-profile official in the country this month. The Taliban claimed responsibility for the attack on the mayor, who held dual citizenship in Afghanistan and the United States.

The killing came two weeks after a suicide bomber used the same disguise to attack senior mullahs at a memorial for the former provincial chairman of Kandahar, Ahmed Wali Karzai, who was also assassinated, heightening concerns that the tenuous security gains in the violent south are faltering despite months of intensified fighting by NATO and Afghan forces.

The mayor, Ghulam Haider Hamidi was killed outside his office in central Kandahar when the bomber blew himself up, and one other person was wounded, said Zalmay Ayoubi, the spokesman for the provincial governor, Tooryalai Wesa.

The Taliban said the attack was retaliation for the mayor’s campaign to force squatters to leave government land.