The death toll from a massive suicide bombing targeting Christians gathered on Easter in the eastern Pakistani city of Lahore has risen to 70 as the country starts observing three-day mourning period following the attack.

A breakaway faction of the Pakistani Taliban, which has sworn allegiance to the Islamic State group, claimed responsibility for Sunday's attack in Gulshan Iqbal Park.

Jamaat-ul-Ahrar's spokesman Ahsanullah Ahsan told The Associated Press the suicide bomber deliberately targeted the Christian community. Some 300 people were wounded in the explosion.

In the capital, Islamabad, the army fanned out Monday around the Parliament and other strategic points to prevent riots by militant protesters who have been rallying there since the previous day.