Unknown gunmen shot dead an American aid worker and his local driver in Pakistan's volatile northwest on Wednesday, officials and police said.

The attack occurred in University Town, an upscale area of the main northwest city of Peshawar where a top U.S. diplomat was attacked just a few months ago, police official Arshad Khan said.

U.S. Embassy acting spokesman Wes Robertson declined to identify the American or say what he was doing in the area other than to say he was not a diplomat.

However, a Western security official in Peshawar said the slain American worked for a development organization with projects in the northwest. The security official spoke on condition of anonymity because he is not authorized to speak to media.

He said the American's car was blocked in a narrow lane by the assailants' vehicle, who then opened fire with automatic weapons.

Pockets of Pakistan's northwest have become safe havens for Al Qaeda and Taliban operatives involved in attacks on U.S. and NATO forces across the border in Afghanistan.

Peshawar has been hit with suicide bombings and other violence.

In August, Lynne Tracy, the top U.S. diplomat in northwestern Pakistan, narrowly survived a gun attack on her armored vehicle in the University Town area.

Earlier this year, Pakistan staged a military operation in a nearby Khyber tribal region after concerns about rising militant activity around the dusty, sprawling city.