Islamabad: A police officer and three civilians were killed in a suicide attack near Pakistan's Baluchistan Constabulary truck in Quetta's Baleli area, media coordinator for the area's Health Department, Dr Waseem Baig, confirmed the number of fatalities.

According to the Dawn, the media coordinator said that in the attack, 27 others including 20 policemen were also injured.

Quetta Deputy Inspector General of Police (DIGP) Ghulam Azfar Mahesar told reporters at the site of the attack that the explosion took place near a police truck which was on its way to provide security to polio workers.

"Due to the impact [of the blast], the vehicle toppled and fell into a ditch," he stated.

The official further informed that a total of three vehicles were hit in the blast, which were a police truck, a Suzuki Mehran and a Toyota Corolla. "Looking at the crime scene and given that the truck toppled, it is estimated that 25 kilogrammes of explosives were used [in the blast]."

Mahesar added that the wounded have been moved to the Civil Hospital Quetta, reported Dawn.

Soon after the attack, the banned Tehreek-i-Taliban Pakistan (TTP) claimed responsibility for the attack.

The blast comes a day after the militant group called off its ceasefire with the government and asked its combatants to carry out attacks across the country.

According to the TTP statement, they called off the ceasefire agreed with the government in June, reported Dawn.

"As military operations are ongoing against mujahideen in different areas [...] so it is imperative for you to carry out attacks wherever you can in the entire country," said the statement.

TTP, a separate entity from the Taliban in Afghanistan but sharing a similar Islamist ideology, have been responsible for hundreds of attacks and thousands of deaths since emerging in 2007.

The decision, it stated, was taken after "the military organisations launched a series of non-stop attacks in Bannu's Lakki Marwat district," added the statement.

Meanwhile, Pakistan Prime Minister Shehbaz Sharif strongly condemned the incident and directed authorities to initiate an investigation into the attack.

"Eliminating polio virus from the country is amongst the top priorities of the government and we will not rest until polio is completely eradicated," PM Shehbaz vowed, asserting that "evil elements" would always fail to harm the anti-polio campaign in the country.

In a statement issued by the Aiwan-e-Sadr, President Arif Alvi condemned the attack and extended condolences to the bereaved families, Dawn reported.

He said that children were Pakistan's most valuable asset and the government was determined to protect them from diseases such as polio. "The State will not allow anti-social elements to interfere in the mission of complete eradication of polio," he promised.

The president also paid tribute to the policemen and health officials working for the eradication of polio.