Security officials inspect the wreckage of a police vehicle after the attack on the vaccination team

Eleven police officers died and 12 were injured when two bombs exploded within minutes of each other as part of an attack on a polio vaccination team in northwest Pakistan, police said.

According to police official Nawabzada Khan, six tribal police officers were wounded when the first bomb struck an escort vehicle in the Lashora village in Khyber Pakhtunkhwa province today.

A second bomb killed 11 and wounded six officers who had been dispatched to help those injured in the first explosion. He said gunmen also opened fire on the guards, triggering a shootout.

The attack lasted an hour and when rescuers approached the scene the gunmen also attacked them, according to Khan Faraz, an official in the Jamrud area of Khyber, a rugged tribal