Gunmen have shot dead a policeman escorting a polio team in the southern Pakistani city of Karachi.
The attack took place in the lawless Orangi area. Vaccination efforts have been suspended in the city.
Media reports said the attackers, who were on a motorcycle, fled when police returned fire.
Pakistan is one of only three countries where polio remains endemic. Militants say polio teams are spies or that the vaccine causes infertility.
More than 60 polio workers or police guarding them have been killed in the country in the past two years.
Last year, more than 300 polio cases were confirmed in Pakistan, the highest figure in 16 years.