Feroz Shah, police chief for Charsadda district, said: "At least 50 people have been killed and dozens were injured in the attack. I fear the death toll may rise further."
"The bomber was among the people, who were offering Eid prayers," Muhammad Sharif Virk, a senior police official said. "He was standing in the second row behind the former interior minister."
Shaukat Ali, 26, who survived the blast, said: "We were saying prayers when this huge explosion occurred."
"It almost blew out our ear drums. Then it was it was like a scene from Doomsday," he said. His white cloak and pants were torn and spattered with blood.
Dozens of wounded were taken to the hospital in Peshawar, the capital of Pakistan's North West Frontier Province.
The hospital was chaotic as injured arrived in pickup trucks, ambulance sirens wailed and wounded screamed for help.
|Friday's attack was the second against Sherpao|
in the last eight months [AFP]
It was the second suicide attack that apparently targeted Sherpao in eight months.
Kamal Hyder, Al Jazeera's correspondent in Pakistan, said: "It was widely expected that there would be more attacks against Aftab Khan Sherpao because of his close association with President [Pervez] Musharraf [and] with the so-called war on terror."
Sherpao belonged to Musharraf's government, which was disbanded ahead of January elections.
Hyder said: "Many people hold him personally responsible for what happened in the Red Mosque because Aftab Khan Sherpao was indeed the interior minister of the country when that happened."
"He had been warned there would be revenge attacks," Hyder said.
Tariq Azeem Khan, a Pakistani senator, said to Al Jazeera: "I think that this is a direct fallout from what is happening in Afghanistan and our own position on the war on terror.
Khan said that it was difficult to say when such attacks could be contained as the Taliban was still working on the Pakistan-Afghanistan border and elsewhere in Pakistan.
He said more such attacks may be a possibility in the run-up to elections.
Imtiaz Gul, a political analyst, told Al Jazeera that the message from the attacks was "that all those people associated with the war on terror, the policy makers, the decision makers, and those who are involved in the implementation, they are the obvious targets of the militants."
Gul said that he did not see any direct relevance of the attacks to the forthcoming elections, but cautioned that they would be difficult to contained as they were becoming a regional phenomena against Western alliance.
"Only political dialogue with the militants forces or these who support these forces perhaps could bring about any change and contain these attacks."
Friday's blast comes amid a surge in violence since security forces launched an assault on the Islamabad mosque in July, which had become a refuge for hardline religious students.
More than 800 people have died in the ensuing reprisal attacks across the country, with about half of them killed in suicide bombings.
Musharraf, a key ally in the US-led "war on terrorism", cited growing lawlessness as a main reason behind imposing emergency rule on November 3. He lifted emergency rule on December 15.
Source: Al Jazeera and agencies