Gunmen kidnapped an Iranian diplomat after killing his guard Thursday in Peshawar, a day after an American aid worker was shot dead in the volatile city in northwest Pakistan.

Authorities cordoned off the city's main roads and were trying to trace the kidnapped Iranian, police official Mohammed Manzoor said. Officials at the Iranian Embassy in Pakistan's capital, Islamabad, did not immediately respond to requests for comment.

Pakistan has experienced a wave of violence in recent years, especially in its northwest where Al Qaeda and Taliban militants have found hideouts. Several foreigners have been kidnapped in the region in recent months.

Until recently, Peshawar, the regional capital, was considered relatively safe. But residents say criminality as well as militancy appears to be on the rise, and that it was possible the Iranian was kidnapped for ransom.

Iran and Pakistan are Muslim neighbors with generally cordial relations, though unlike Pakistan in the 1990s, Iran did not support the Taliban regime in Afghanistan.

U.S. efforts to help reduce militancy in Pakistan's northwest through development programs were dealt a blow Wednesday when gunmen shot and killed American Stephen Vance, who worked for CHF International, a U.S.-based aid group.

The group was implementing U.S. government-funded schemes to pump $750 million over five years into developing basic infrastructure such as wells, clinics and roads in the impoverished tribal areas bordering Peshawar.

Vance was attacked as he was being driven from his home to his office in University Town, an upscale area of Peshawar where a top U.S. diplomat narrowly escaped a gun attack a few months ago. Vance's Pakistani driver also was killed.

The northwest's semiautonomous tribal regions are considered possible hiding places for Usama bin Laden and Al Qaeda No. 2 Ayman al-Zawahri. Militants use pockets of the northwest as staging grounds for attacks on U.S. and NATO troops in Afghanistan.

The U.S. has stepped up missile strikes on militant targets in the tribal areas, prompting protests from Pakistani leaders as well as threats of militant revenge.