At least 15 people were killed in a suicide bombing outside a U.N.-backed polio vaccination center in the city of Quetta, Pakistan, on Wednesday, authorities said.
The bomb detonated near a police van that had arrived at the center to escort staff working on an immunization program for children under 5, Reuters reported.
Most of those who died are believed to have been members of the Pakistani security forces, according to BBC News.
Ahsan Mehboob, the provincial police chief, confirmed to Reuters: "It was a suicide blast, we have gathered evidence from the scene. The police team had arrived to escort teams for the polio campaign."
"According to an initial investigation, police and security forces resisted a suspect who tried to get inside the building when the powerful blast occurred," provincial Interior Minister Sarfraz Bugti told The Guardian.
Two separate militant groups — the Pakistani Taliban and Jundallah, which is Taliban-linked and pledged allegiance to ISIS — have reportedly claimed responsibility for the attack, according to Reuters.
Polio vaccination programs have been targeted by militants in Pakistan in the past, and police escorts at the centers are routine. Some militant groups believe the anti-polio campaign is part of a Western conspiracy designed to sterilize children, The Guardian said.
Pakistan is one of just two countries on the planet where the disease is still endemic. The other is Afghanistan.
Francis Whittaker is a homepage editor for BuzzFeed News and is based in London.
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