Sargodha is in Punjab, Pakistan's most populous province and its political heartland.

The region has increasingly come under attack by al-Qaeda and Taliban, which have logistics and training centres close to the Afghan border several hundred kilometres away.

More than 40 people were killed in twin suicide bombings at a Sufi shrine in the provincial capital Lahore this month.

And more than 80 people were killed in twin attacks in late May on Ahmadis, a religious minority sect declared non-Muslims in Pakistan.