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 explosion ripped through a police van that had just arrived at the centre.
"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."
The latest attack comes as a suicide bomb 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.
Pakistan and neighbouring Afghanistan are the only two countries in the world where polio remains endemic, the World Health Organization said.
Teams in Pakistan have been working to immunize children against the virus are often targeted by Taliban and other militant groups, who say the campaign is a cover for Western spies, or accuse workers of distributing vaccines designed to sterilize children.
The campaign to eradicate the virus in Pakistan has had some recent success, with new cases down last year, but violence against vaccination workers has slowed the effort.