The bomber attacked Maulvi Nazir in Wana, the main town in the South Waziristan tribal area, as he was arriving at an office he uses to meet with locals and hear their complaints, said the commander's spokesman, Maulana Ameer Nawaz. Nazir was not critically wounded, said Nawaz.
Nazir was one of over a dozen people wounded in the attack, said Pakistani intelligence officials and a local government administrator, speaking on condition of anonymity because they were not authorized to talk to the media.
They initially reported that three people died, but later raised the number to seven after some of the critically injured died of their wounds.
No group has claimed responsibility for the attack, but suspicion is likely to fall on the Pakistani Taliban, which has been waging a bloody insurgency against the government for the past several years and has jockeyed with Nazir for power in South Waziristan.
The tribal area was the Pakistani Taliban's main sanctuary until the army launched a large ground offensive in 2009 and pushed many of them out.
Nazir is widely believed to have cut a deal with the army ahead of the offensive that allowed him to stay in South Waziristan as long as he remained on the sidelines. The militant commander has in the past focused his fight against U.S.-led forces in Afghanistan, not against the Pakistani state.
Nazir had been running a secret campaign in recent weeks to push the Pakistani Taliban and foreign militants allied with them out of Wana and the surrounding areas, said intelligence officials.
Nawaz, the militant commander's spokesman, said the suicide bomber who attacked Nazir appeared to be a 15- or 16-year-old boy.
"The moment the chief got out of his vehicle, the boy ran toward him and detonated his explosives," Nawaz told The Associated Press by telephone.
Yar Mohammad, a resident of Wana who witnessed the attack, said the blast was huge.
"I'm seeing smoke everywhere," he said.
Nazir's fighters retaliated after the attack by killing two Pakistani Taliban militants in the main market in Wana, said intelligence officials. There were also reports of Nazir's fighters attacking Pakistani Taliban militants in the nearby village of Kari Kot, they said.