Many of the bomb victims were children at a funfair in the Lahore park. Photo: AFP

Punjab's law minister said those held were among more than 5,000 questioned in a sweeping counter-terror offensive.

Weapons and ammunition have also been seized in raids by security forces.

Taliban splinter group Jamaat-ul-Ahrar said it carried out the attack against Christians celebrating Easter, although most of those killed were Muslims.

The area around Gulshan-i-Iqbal park was more crowded than usual, as members of Lahore's minority Christian community had gathered to celebrate Easter at a funfair there.

At least 29 of the victims were children. Another 300 people were injured, with officials saying they expected the death toll to rise.

"There are no militant safe-havens or no-go areas in Punjab," law minister Rana Sanaullah told a news conference in Lahore.

He said 56 intelligence operations had been jointly carried out by police, paramilitary, army and intelligence forces.

Both Pakistan's prime minister and the powerful army chief have vowed to bring the attackers to justice.

Reports say the military is preparing to launch a new crackdown in Punjab, Pakistan's most populous and wealthiest province - and the heartland of PM Nawaz Sharif's support.

Jamaat-ul-Ahrar's spokesman mocked Mr Sharif on Tuesday, saying that war had "reached his doorstep".