India, July 30 -- Nine security officials and 15 militants were killed and 28 police personnel injured during an operation in northwest Pakistan following an attack on a police checkpoint, police said on Thursday.

The operation was launched in retaliation for Wednesday, 29 July's attack on a police checkpoint in Hangu district of Khyber Pakhtunkhwa province.

Reinforcements were dispatched after the attack, but the vehicle carrying additional personnel also came under militant fire, police said.

According to a police spokesperson, nine police personnel were killed and 28 others injured during the operation. The intense exchange of fire also killed 15 militants and injured several others, police said.

Khyber Pakhtunkhwa Chief Minister S...