According to letter communicated to Sindh Home Ministry from intelligence agencies, terrorists might target school vans in the provincial capital.
It said militants could plant a magnet bomb in school vans in an attempt to target schoolchildren in avenge to execution of their accomplices.
The letter, addressed to Police, Rangers, and school administrations, said van drivers must not leave their vehicles anywhere for security reasons.
It said drivers must keep their vehicles away from any metal material at the time of parking.
In a deadliest attack to retaliate against army operation in North Waziristan, Taliban gunmen stormed a school in Peshawar last week and massacred 148 people including 132 children, drawing widespread condemnations from across the world.