ISLAMABAD: A grenade was hurled near a school in Pakistan's Karachi city Tuesday. No casualties were reported, a media report said.
The motorcycle borne attackers, however, left a threat letter before fleeing.
A police official said the attack occurred in a lane between two sections of the school, Dawn online reported.
As the school was closed, there was no student or staff in the premises, he added.
Provincial Education Minister Nisar Ahmed Khuhro has sought a report over the incident from Karachi police.
The government had extended winter vacations in schools for security reasons following the Dec 16 Peshawar school attack in which schoolchildren were killed.
The Sindh government had announced that only those schools should reopen where foolproof security arrangements have been ensured. It also decided to implement a short-term security plan for all educational institutions in the city.