Pakistani security officials examine the site of a bomb blast near a polio vaccination centre in Quetta on January 13, 2016. Image Credit: AFP

QUETTA, Pakistan: A suicide bomber blew himself up outside a polio vaccination centre in the southwestern Pakistani city of Quetta on Wednesday, killing at least 15 people, mainly police, officials said.

The policemen had been gathering outside the centre to accompany polio workers for the third day of a vaccination campaign, which are frequently targeted by militant attacks in Pakistan, in the violence-wracked province of Balochistan, of which Quetta is the capital.

"There are 15 dead, including 12 police, one paramilitary, and two civilians," a local police official told AFP.

Sarfaraz Bugti, Balochistan home minister added: "So far 15 people have been injured in the blast seven of whom are in critical condition."

An AFP reporter at the site saw three burnt out vehicles that had been blown up in the explosion, while human remains lay strewn across the ground, walls, and electric poles along with items of clothing including the caps and shoes of policemen.

Some officials had begun to gather evidence from the scene while others were collecting body parts to put in bags.

Eye-witness Shabir Ahmad, a 32-year-old police constable, told AFP he had been deployed to protect a polio vaccination team that was due to leave for various neighbourhoods of Quetta at 10am.

"Suddenly there was a loud bang and I fell to the ground, I could not see anything, there was dust everywhere," he said.

"Then I heard people screaming and sirens of ambulances," he continued, adding he had received shrapnel wounds to his stomach, hands, legs and feet.

The latest attack comes as a suicide bombing struck near the Pakistani consulate in Afghanistan's Jalalabad city, killing two people just days after four-country talks aimed at reviving Taliban peace negotiations commenced in Islamabad.

Polio endemic

Pakistan is one of only two countries where polio, a crippling childhood disease, remains endemic. Attempts to eradicate it have been badly hit by militant attacks on immunisation teams that have claimed nearly 80 lives since December 2012.

While there was no immediate claim of responsibility for Wednesday's attack, Islamist groups including the Taliban say the polio vaccination drive is a front for espionage or a conspiracy to sterilise Muslims.

In 2014 the number of polio cases recorded in Pakistan soared to 306, the highest in 14 years.

The most recent attack came in November last year, when unknown gunmen shot and killed the head of an immunisation programme in the Khyber Pakhtunkhwa district of Swabi.

Islamist opposition to all forms of inoculation mounted after the CIA organised a fake vaccination drive to help track down Al Qaeda's former leader Osama Bin Laden in the Pakistani garrison town of Abbottabad.

The terror chief was killed during a US special forces raid in 2011.

Balochistan, Pakistan's largest but most impoverished province, is also home to a raging insurgency that has claimed the lives of hundreds of soldiers and militants since it re-ignited in 2004, with rebels often attacking government installations and personnel.

The province's roughly seven million inhabitants have long complained they do not receive a fair share of its gas and mineral wealth.