"The remote-controlled bomb hit the convoy and damaged several vehicles. Two people later died in hospital," Nisar Ahmed Tanoli, a senior police official told AFP, adding that Wazir was among six injured.
Bannu is close to the lawless tribal area along the Afghan border where Taliban and other Islamic militants have hideouts.
Nobody immediately claimed responsibility. But the umbrella Tehreek-e-Taliban Pakistan has made death threats against politicians from the secular ANP, which ruled Khyber Pakhtunkhwa from 2008 until this year.
Violence has been increasing in the northwest as Pakistan prepares to hold a general election on May 11, which will mark the country's first democratic transition of power.
Pakistan says more than 35,000 people have been killed as a result of terrorism in the country since the 9/11 attacks on the United States.