A suicide bombing in Pakistan's Balochistan province on Wednesday killed four people and injured 26?others, including 23?policemen.?

A suicide bomber on Wednesday blew himself near a police truck in Balochistan's Quetta's Baleli area. The truck was carrying security personnel to protect polio workers at an ongoing vaccination drive.?

The banned Tehreek-e-Taliban Pakistan (TTP) group claimed responsibility for the attack. The attack came just two days after the group announced the end of its ceasefire with Pakistan government and declared the launching of nationwide attacks. The TTP said the attack was in retaliation for the killing of Abdul Wali, also known as Omar Khalid Khurrassni. He was killed in Afghanistan in August.

Pakistan, along with neighbouring Afghanistan, is the only country in the world where polio is still prevalent, according to the World Health Organization (WHO). Polio vaccination in Pakistan is often often opposed by religious hardliners. There have been earlier disruptions and attacks on polio workers in Pakistan and Afghanistan.

Quetta Deputy Inspector General of Police (DIGP) Ghulam Azfar Mahesar confirmed the attack and said that 20 policemen were injured in the attack.

"Looking at the crime scene and given that the truck toppled, it is estimated that 25 kilograms of explosives were used," said Mahesar, adding that a total of three vehicles were hit in the blast.

Mahesar said that the explosion was a suicide attack as they have found the remains of a suicide bomber near the crime scene.

Preliminary police investigations showed that a rickshaw hit the police truck. Authorities have declared an emergency in the hospitals of Quetta to treat the victims.

What's TTP, what are its goals?

The Tehrik-e Taliban Pakistan (TTP) is a banned Islamist militant group in Pakistan. It's an umbrella organisation formed in 2007. It's often also called Pakistan Taliban.

The TTP's stated objectives are to take control of Pakistan's tribal areas from the Pakistani state and implement its strict interpretation of Islamic law there.

"TTP’s stated objectives are the expulsion of Islamabad’s influence in the Federally Administered Tribal Areas and neighboring Khyber Pakhtunkhwa Province in Pakistan, the implementation of a strict interpretation of sharia throughout Pakistan...TTP leaders also publicly say that the group seeks to establish an Islamic caliphate in Pakistan that would require the overthrow of the Pakistani Government," says US Office of Director of National Intelligence's (DNI) National Counterterrorism Center on TTP.

Praise of polio workers, polio eradication pledge

Prime Minister Shehbaz Sharif condemned the incident and directed the authorities to initiate an investigation into the attack. He expressed grief and sorrow over the loss of life, according to the state-run Radio Pakistan.

Sharif also said that polio workers across the country were fulfilling their responsibilities without caring for their lives.

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

President Dr Arif Alvi also condemned the attack and prayed for the forgiveness of the deceased and the recovery of the injured. 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 said.

Former Prime Minister and Pakistan Tehreek-e-Insaf (PTI) chief Imran Khan also expressed deep grief on the attack and prayed for the speedy recovery of the injured people.

Rising attacks on polio workers

Attacks on workers of the anti-polio vaccination drives in Pakistan have increased in recent times.

In March this year, gunmen in northwestern Pakistan shot and killed a female polio worker as she was returning home after taking part in the country’s latest anti-polio campaign.

In January last year, armed gunmen shot dead a police officer guarding a team of polio vaccine handlers in northwestern Pakistan.

(With PTI inputs)