Four people were killed and more than 20 wounded in a suicide bombing in south-west Pakistan on Wednesday, two days after Pakistani Taliban called on its fighters to launch attacks across the country.
A child was among the victims of the attack targeting a police patrol in Quetta, spokesman Abdul Haq told Reuters.
At least 15 police officers were among those wounded in the explosion, confirmed by Mr Haq to be a suicide bombing, as police prepared to escort a polio vaccination team in the provincial capital of Balochistan province.
Tehreek-e-Taliban Pakistan (TTP) have claimed responsibility for the attack, which they said was to avenge the killing of their former spokesman in a bombing in Afghanistan’s Paktika province in August.
It comes only days after the group ended a months-long ceasefire with Islamabad and called on its members to wage attacks across Pakistan.
“The target of the attack was the police truck, however, two more [civilian vans] which were on the road were also hit by the blast,” Ghulam Azfar Mahesar, director general of police (DIG), told The National.
"The police van was hit by a small vehicle [which has yet to be confirmed] in which the suicide bomber was sitting.”
The DIG said about 25kg of explosives were used. An investigation was on Wednesday under way, with evidence being gathered from the scene.
Earlier this month, the TTP killed six police officers in an ambush on a patrol in the north-west of the country. While separate from the Afghan Taliban, its militants share the same ideology and have launched regular attacks in recent months despite the ceasefire signed in June.
On Tuesday, Pakistan's Foreign Affairs Minister, Hina Rabbani Khar, visited Kabul amid cross-border violence blamed on the group. Islamabad said a "range of issues" was discussed but did not mention security.
The Afghan Taliban has been facilitating talks between Islamabad and the Pakistan-based militants for the past year.
Rifat Orakzai, a veteran journalist who focuses on militant groups, said the TTP had stopped suicide attacks because the Afghan Taliban had banned the practice on the grounds it was “un-Islamic”. But Wednesday’s attack, he added, showed that the TTP could be set to use similarly violent tactics again.
Mr Orakzai said it was a strategy of the Afghan Taliban and TTP to carry out attacks to press home their demands during peace talks.
"This is a very challenging task for the Pakistani officials because on one side the peace talks have ended and on the other hand the banned organisations and their leaders are in Afghanistan and the Pakistani government can’t take any action against them as it will create problems with the Afghan government,” he said.
The TTP was founded in 2007 by extremists who had fought alongside Afghan Taliban militants in the 1990s.
The government in Islamabad claims Kabul has allowed the group to gain a foothold in border areas. Earlier this month, it opened a border crossing connecting Balochistan province with Afghanistan after clashes with Afghan security forces had led to its closure.
Pakistan has recorded a 50 per cent surge in militant attacks since the Taliban takeover of Afghanistan, the Pak Institute for Peace Studies says.
Prime Minister Shehbaz Sharif strongly condemned the incident, expressed grief and sorrow over the loss of life and prayed for the speedy recovery of the wounded.
He said polio workers across the country were fulfilling their responsibilities without concern for their own lives. For this, he said, Pakistan pays tribute to their service.
The PM added that eliminating polio from the country was among the top priorities of the government and "we will not rest until polio is completely eradicated".
Balochistan's chief minister, Abdul Quddus Bizenjo, also condemned the attack and instructed authorities to provide those injured with the best medical treatment.
The latest bombing in Quetta comes amid a nationwide push to vaccinate 13 million children against polio in "high-risk" areas of the country.
Pakistan and Afghanistan are the only countries in the world where wild polio is still endemic.