A roadside bomb targeting a bus has killed at least 10 people in the northwestern Pakistani district of Kurram, local officials say.
The explosion occurred in central Kurram as the vehicle travelled to the town of Sadda, about 250km west of the capital Islamabad, early on Tuesday morning, Majidullah, a local administration official, told Al Jazeera.
"There were about 23 passengers in the van, and there was a bomb placed on the roadside near the village of Godar, he said, adding that at least 13 people were also wounded.
"Security forces have now initiated a search operation in the area."
Another local administration official confirmed the death toll, speaking on condition of anonymity.
Kurram is located along Pakistan's northwestern border with Afghanistan, and has seen a series of attacks in recent days, often targeting the district's sizeable Shia Muslim minority.
No group immediately claimed responsibility for the attack.
In a statement, the military said it had dispatched a transport helicopter to move those in need of critical medical care.
The wounded were being treated at hospitals in Sadda, Parachinar and Peshawar, said Majidullah.
Last month, a bomb targeting a Shia mosque in Kurram's main town of Parachinar killed at least 10 people and wounded dozens more.
In January, a bomb explosion ripped through a busy Parachinar vegetable market, killing at least 22 people.
The Pakistani Taliban claimed responsibility for both of those attacks. Pakistan has been battling the group - an umbrella organisation of armed religious groups - since 2007, and has launched a series of military operations against them, including one in Kurram district that concluded in 2011.
In response to the latest spate of attacks, Kurram's residents have formed tribal militias to work with Pakistan's security forces to secure the area. They have dug trenches around Parachinar, as well as establishing bunkers at strategic locations.
This area, however, had no increased security, according to local official Majidullah.
"This area is in central Kurram - there is no increased security there," he said.