A girls' school in Pakistan has received anonymous threats that its building will be bombed if the teachers and students did not start wearing veils and burqas.

The principal of the government high school in Mardan received a letter from an unidentified source, which threatened that the school would be bombed within seven days if students and teachers did not start wearing veils, Pakistan's Online news agency reported.

Security personnel have been deployed around all girls' schools after the school administration informed about the letter to the local authorities.

It is believed that the letters are being sent by associates of Al-Qaeda leader Abu Farah, who was arrested from the same area.

Similar letters were also sent to some schools in Peshawar, and as a result, two schools were closed down and security for others was increased.