Dozens injured in latest violence during gov't-Taliban peace talks.
Kareem Khan was due to testify about the impact of strikes on Pakistan.
Explosions cut gas supply to country's most populous province.
Victims included sleeping women and children.
The two sides are due to start charting a "roadmap" for peace talks.
Group negotiators are insisting on the importance of implementing Sharia, or Islamic, law in Pakistan; also demanding that U.S.-led foreign troops withdraw from neighboring Afghanistan.
Gov't cancelled preliminary peace talks scheduled to start Tuesday.
Peshawar, Pakisan remains a reservoir of polio.
The son of Benazir Bhutto says politicians must "wake up" to threat posed by groups such as the Taliban.
Briton of Pakistani origin had written letters claiming to be a prophet.
