Four people were killed and 26 wounded when a suicide bomber targeted a police truck in western Pakistan assigned to protect polio workers, officials said, an attack claimed by the Pakistani Taliban.
The November 30 attack occurred in Quetta, the capital of Pakistan's restive Balochistan Province bordering Afghanistan and Iran, where both Islamist and separatist militants operate.
Officials said the blast killed three civilians -- one woman and two children -- from the same family who were traveling nearby in a car. A police officer was also killed in the attack.
Police official Azfar Mahesar told RFE/RL that the police were guarding polio vaccinators.
Twenty-three of the 26 people wounded were police officers traveling in the truck escorting the polio vaccinators.
Polio-vaccination teams are routinely escorted by police in the western regions.
Pakistan on November 28 launched a weeklong immunization campaign aiming to inoculate over 13 million children living in "high-risk districts."
The Pakistani Taliban -- known as Tehrik-e Taliban Pakistan (TTP) -- claimed responsibility for the "martyrdom attack."
Pakistani President Arif Alvi, Prime Minister Shahbaz Sharif, and other officials in separate statements condemned the attack.
On November 28, the TTP declared an end to a shaky cease-fire with Islamabad declared over the summer and ordered nationwide attacks to resume.
The truce between the Pakistani government and the TTP was agreed in June after Afghanistan's Taliban-led government took a prominent role in brokering peace talks. The TTP follows the same hard-line interpretation of Sunni Islam as their Afghan counterparts, but has a different organizational setup.
Afghanistan and Pakistan are the only countries in the world where wild polio is still endemic.