At least 12 people have been killed and 25 injured in what police say is a suicide bomb attack in the Hangu district of north-west Pakistan.
The attack targeted a convoy of 140 vehicles travelling from Tall in the Hangu district to the town of Parachinar in the Kurram region.
No-one has yet said they carried out the attack.
Pakistan's North West Frontier Province has witnessed numerous bombings by insurgents over the past year.
A suicide attack on a police station in the Karak area of north-west Pakistan killed three people last week.
Volatile region
Police said that the bomber detonated explosives near a bus full of passengers.
The convoy was carrying groups of people as well as vehicles loaded with general provisions and other trade goods. Most of the passengers in the convoy were Shia Muslims.
The Parachinar and Orakzai region is home to a large number of Shia Muslims and the area has suffered from sectarian violence in the past.
The Tall-Parachinar road was closed to all traffic for nearly two years in 2008 and 2009 because of Taliban activity in the area and the frequency of attacks on Shia Muslims in the area, correspondents say.
The road was re-opened about two months ago and traffic currently moves in convoys guarded by paramilitary security forces.
Hangu borders Pakistan's volatile semi-autonomous tribal regions, where a number of militant groups are thought to be operating.
But anti-militant operations by security forces in the area has improved security, correspondents say.
At least twelve civilians have died and over 25 wounded in a suicide bombing in the  of north-west Pakistan, Thursday night. A convoy of 140 vehicles running from , in Hangu District to the town of  in , FATA was targeted.

The victims, some of them women, were at a petrol station in Hangu. The wounded were taken to adjoining hospitals.

According to police, the attacker detonated a bomb near a fully loaded bus. The convoy carried several people, vehicles filled with provisions and commodities for trading. A majority of the people in the group were Shia Muslims. 

No one has yet claimed responsibility for the attack. Several insurgents have attacked the country's North West Frontier Province in the last year. Earlier, three died in another suicide attack on a police station in Karak, located in the same area.

Many Shi'as dwell in the Parachinar and Orakzai area which has been home to violence in the past. The Tall-Parachinar road was closed to the public in 2008 and 2009 due to Taliban activity. The latter targeted Shia Muslims, sources say. The road was re-opened about two months ago, with convoys guarded by security forces forming the bulk of the traffic.

Hangu borders Pakistan's tribal regions, where several militant groups are believed to be operating. However, security forces say that arrangements have improved from the past.