At least seven policemen, three of whom were guarding polio workers, have been killed, following an attack by gunmen, in Pakistan.
Seven Pakistani policemen, three of whom were guarding polio workers, have been killed in Karachi, officials say.
Eight gunmen on motorcycles fired at a group of three guards and later at a van containing four officers, officials told the Pakistan Tribune.
Islamist militants oppose vaccination, saying it is a Western conspiracy to sterilise Pakistani children.
In January, 15 people were killed in a bomb attack on a vaccination centre in the south-western city of Quetta.