The bomb reportedly was detonated just after Sherpao had finished making a speech at the meeting in the town of Charsadda, about 35 kilometers north of the provincial capital of Peshawar.
Provincial Police Chief Sharif Virk said the bomber detonated his explosives close to the podium from which Sherpao had been speaking.
Two of Sherpao's bodyguards who attempted to stop the suicide bomber from approaching the minister reportedly were among those killed.
Police say at least 24 others were hospitalized with severe injuries.
Sherpao was taken to a hospital, but there was no immediate word on his condition. His son was reportedly also among the injured.
Meanwhile, Pakistani police investigating the attack say they have recovered the severed head of the bomber and that he appeared to be an Afghan national.
Pakistan's Northwest Frontier Province has a large community of Afghan refugees, with many living at camps in the troubled region.
Islamabad on April 15 became to forcibly repatriate Afghan refugees who had failed to legally register their presence in Pakistan by that date.
Pakistan has been hit by five suicide bombings this year that have killed more than 50 people.
Today's attack came just hours after Washington announced that it had detained a senior Al-Qaeda suspect involved in two failed assassination attempts against Pakistani President Pervez Musharraf.
(compiled from agency reports)