PESHAWAR Pakistan (Reuters) - Seven people were killed and at least 11 wounded when an explosive device ripped through a passenger bus travelling outside the volatile Pakistani city of Peshawar on Thursday, a hospital spokesman and police said.
The attack took place against the backdrop of a large military operation in Pakistan's tribal North Waziristan region targeting Taliban hideouts in the lawless area on the Afghan border - a campaign militants have vowed to avenge.
"In the last 24 hours a bomb disposal squad has detonated six bombs in various localities of Peshawar," Shafqat Malik, a senior police officer, told reporters at the site of the blast.
"This is the seventh which went off and 5kg (11 lb) of explosives were used in the bomb."
The driver of the bus, Shams-ur-Rehman who survived the attack, told investigators that an old man was spotted sitting with an old bag on a rear seat and that the device exploded shortly after he got off.
A police investigator, speaking on condition of anonymity, said it might have been a sectarian attack as most passengers in the bus were Shi'ite Muslims. Radical Sunni Muslim militants frequently attack Shi'ites whom they see as infidels.
No one immediately claimed responsibility for the attack.
(Reporting by Hameedullah Khan Writing by Maria Golovnina; Editing by Andrew Heavens)