Investigators arrested four suspects, including the alleged mastermind, in Friday's Islamabad bombing that killed 31 and injured 169.

The Islamic State group claimed responsibility for ‍the attack, the deadliest of its kind in Islamabad in more than a decade.

The reforms, to be introduced to parliament this week, will include tougher penalties for displaying terrorist symbols, reciting certain chants, and wilfully damaging places of worship.