Peshawar, Pakistan : A police officer says a bomb exploded in northwest Pakistan near a vehicle carrying officials taking part in an anti-polio campaign, killing at least six people.
Police official Samiullah Khan says Monday morning's bomb killed four police officers and two members of a local peace committee riding in the van.
Khan says the bombing happened in the village of Malikhel, outside the provincial capital of Peshawar.
Pakistan is one of three countries in the world where polio is still endemic.
Part of the reason that it is still prevalent is that militants who oppose the campaign often target the workers and threaten people who want to get their kids vaccinated.