A bomb killed a Pakistani religious leader and two of his guards during a celebration at a northwestern shrine on Monday, police said, as officers prepared for a militant backlash over a continuing military operation.
Pakistan launched a military offensive in June to seize control of the Taliban stronghold of North Waziristan, a remote mountainous region on the border with Afghanistan.
The United States had long urged Pakistan to move against militant hideouts there, saying the area was used to prepare attacks in both Afghanistan and Pakistan.
Recent weeks have been quiet as Muslims observed the holy month of Ramadan by fasting during the day. But police have said they expect attacks to increase after Ramadan ended last week.
Monday's bomb attack took place as a crowd of thousands gathered at a Sufi shrine near the city of Dera Ismail Khan where the religious leader, Faqir Jamshed, was presiding at a function.
The attack killed Jamshed and his guards, said Zahoor Khan, police chief in the restive area.
"We foresee such types of incidents will increase after Ramadan," said Sadiq Balochi, the district police officer for Dera Ismail Khan.
"We are ready for any such thing. We are in close coordination with the army and all intelligence agencies. Joint patrolling has been enhanced."
Last week, soldiers were deployed to guard key installations in Islamabad, the capital. Security at airports has also been beefed up following a deadly attack on the airport in the southern city of Karachi days before the operation began.
Police patrols have also been stepped up and hundreds of suspected militants arrested around the country, authorities say.
Sufism, a mystical and tolerant form of Islam that emphasises a direct link with god, is coming under increasing attack from hardline Taliban-linked militants in Pakistan.
The Taliban are fighting to impose a hardline Sunni state ruled by strict Islamic law.