In addition to wounding the agents, the explosion killed a Turkish woman and wounded a fifth American, three Pakistanis, a person from the United Kingdom and someone from Japan, authorities said.
None of the agents were critically hurt in the blast, which occurred at 8:45 p.m. local time. The agents' wounds included deep lacerations, concussions and fractures, the source said. The four, who were eating dinner together at the time of the attack, were not believed to have been targeted, the source added. An air ambulance took the agents to a hospital.
Government officials have not said who they believe is responsible for Saturday's attack, but they suspect al Qaeda and Taliban-linked militants from Pakistan's tribal region, who have carried out similar attacks in the past.
An FBI spokesman in Washington had no comment, but National Security Council spokesman Gordon Johndroe told CNN that President Bush "appreciates the hard and dangerous work that U.S. officials engage in around the world, and our thoughts are with them and their families as they recover from this attack."
Four FBI agents hurt in Pakistan bombing, source says - CNN.com