(Adds details on attack)
PESHAWAR, Pakistan, June 16 (Reuters) - A bomb planted in a pickup truck killed at least 13 people at a market in northwest Pakistan on Saturday and the death toll could rise, security and hospital officials said.
The target in the town of Landi Kotal appeared to be a tribal leader allied with the government against the Pakistani Taliban, the Islamist militant group blamed for many of the suicide bombings across the country, security officials said.
They had earlier said a car bomb had caused the explosion. Hospital officials said 34 people were wounded.
There was no immediate claim of responsibility.
One security official said a suicide bomber connected with the attack began wandering around the town shortly after the explosion.
"The blast was so powerful, it was heard far and wide and caused damage to nearby buildings," said resident Sher Mohammad Shinwari, adding most of the casualties were fruit and vegetable traders who were beside their roadside push-carts.
The Pakistani Taliban are seeking to topple the U.S.-backed government. Suicide attacks have eased in recent months but there are no signs Pakistan's military has broken the back of the group.
(Reporting by Ismail Khan and Ibrahim Shinwari; Writing by Michael Georgy; Editing by Nick Macfie)