JOIN USSeventy others were injured in the attack at Khar, the main town in Bajaur tribal district where government forces are fighting Taliban and Al Qaeda militants.
Imtiaz Khan, a government official, said that around 300 people were gathered to get food when the bomber struck. "According to initial reports, the bomber was a woman wearing a burqa."
If confirmed it would be only third suicide attack in Pakistan by a woman.
"Forty-two people have been confirmed dead while more than 70 people are injured. Seven to eight people are in critical condition," Afif Khan, a medical officer at emergency department in Khar's main hospital said over phone.
Thousands of families displaced by fighting between Taliban and government forces rely heavily on food provided by the government and the UN World Food Programme.
The bombing came a day after 150 Taliban fighters carried out coordinated attacks on five security posts in neighbouring Mohmand district. Eleven soldiers and 24 militants died, officials said.