The death toll in a bombing at a political rally held by a religious party rose to 45 on Monday, officials said, an attack compounding fears of unrest ahead of a general election due later in the year.
The bomber attacked the gathering of the conservative Jamiat Ulema Islam-Fazl (JUI-F) party, which is allied with the government, in the Bajaur district on Sunday in the northwest, near the border with Afghanistan.
No group has claimed responsibility.
An official at a state-run rescue agency, Bilal Faizi, said the death toll had risen to 45. Of more than 130 wounded people, 61 were under treatment, said government health adviser Riaz Anwar.
A police counter-terrorism wing investigating the blast suspected the IS group was behind it, police said in a statement.
Pakistan has seen a resurgence of attacks by IS militants since last year when a ceasefire between the Pakistani Taliban, the Tehreek-e-Taliban Pakistan (TTP) and the government broke down.
A mosque bombing in Peshawar city in the northwest killed more than 100 people in January but attacks on political parties are rare.
While the TTP and associated groups have been behind most of the attacks in recent months, the group distanced itself from Sunday's attack with a spokesman condemning it.
The JUI-F is an ally of the coalition government of Prime Minister Shehbaz Sharif who denounced the blast as an attack on the democratic process.
Prospects for the general election, due by November, have already been clouded by months of rivalry between main parties and accusations of military involvement in civilian politics. The military denies that.
Thousands in US and Europe protest against Trump, Musk
Two British MPs detained by Israel, British FM says
Israeli attacks on Gaza killed 60 people in 24 hours
Trump fires National Security Agency director
