A suicide bomber blew himself up and killed four people after striking a truck carrying police officers on their way to protect polio workers.
The Pakistani Taliban claimed responsibility for the attack in the southwestern city of Quetta, Pakistan which injured around 27 people, around 20 of whom are police officers.
Ghulam Azfer Mehser, a senior police officer, said the attack happened as they were heading to the polio workers, part of a nationwide vaccination drive launched Monday.
The blast was so powerful that the truck carrying police officers fell into a ravine, killing one officer and three civilians.
Javed Akhtar, an official at the government hospital in Quetta, told Al Jazeera that a four-year-old girl and a woman were among the civilian casualties.
Pakistani President Arif Alvi, Prime Minister Shahbaz Sharif and other officials all condemned the attack and confirmed that Polio prevention work will continue.
Prime Minister Shehbaz Sharif said: "Polio workers are performing their duties to end this disease without fearing for their lives. Ending polio completely is among the top priorities of the government."
The Pakistani Taliban confirmed the attack in a statement saying: “This attack was carried out after the announcement to end ceasefire and was planned to take revenge for the death of Omar Khalid Khorasani. Our attacks will continue."
Khorasani was a senior leader of theirs who was killed in a car bomb blast in Afghanistan in August.
The car blast came a day after Pakistani Deputy Foreign Minister Hina Rabbani Khan travelled to Kabul in Afghanistan to discuss a range of issues with the Afghan Taliban, including the latest threat from the local Taliban.
Pakistan wants Afghanistan's Taliban not to allow the Pakistani militants to use their country to launch attacks.
Earlier this month, the group also hit another police vehicle in Lakki Marwat city in the northwestern province of Khyber Pakhtunkhwa, killing six police personnel.
And nearly 100 people associated with the immunisation campaign in Pakistan have been killed in the last decade, with five attacks this year alone.
Pakistan is one of the two polio-endemic countries in the world along with its neighbour Afghanistan.
Polio vaccination teams are routinely escorted by police in the western regions due to vaccine hesitancy among conservative communities who falsely believe they are an effort to sterilise them.
In the year since the Taliban returned to power in Afghanistan, Pakistan has seen a 50 per cent surge in militant attacks, according to the Pak Institute for Peace Studies (PIPS).