An explosion in a busy vegetable market killed at least 21 people on Saturday in Pakistan's remote northwestern tribal region, an official said.
About 40 others were wounded in the blast in Kurram region, near the border with Afghanistan, said Sajid Hussain Turi, member of the National Assembly from the region.
"We received 21 bodies of the local tribal people killed in the blast," Turi said, adding that there would be a mass funeral and then a demonstration over the attack.
Reports differed on the cause of the explosion.
Turi said a homemade bomb had been planted in a pile of tomatoes and exploded as people gathered in the market in Parachinar, Kurram's main town, early on Saturday morning.
Taliban militants have been active around Parachinar in the past, ad the town has also suffered sectarian tension between Sunni and Shi'ite Muslims.
Another Kurram official, Sabzali Khan, said early reports had suggested that a suicide bomber was responsible for the blast.
An eyewitness, Ashiq Hussain, said he saw bodies strewn around the market and wounded people crying out for help.
"There was no ambulance, and people had to carry the injured in cars and private pickup trucks to the hospital," Hussain told Reuters.
A statement from Pakistan's military said army helicopters had been dispatched to evacuate the wounded.