A roadside bomb has killed two local tribal elders in north-west Pakistan, officials say.
At least one other man was reported seriously injured in the blast near the town of Khar in Bajaur tribal region.
Security officials said the bomb was detonated by remote control. No group has said it carried out the bombing.
It is the latest in a series of attacks blamed on tribal militants. At least 80 people died when the military bombed a school near Khar last October.
Officials said the school was a training camp for militants but locals and religious parties said the victims were civilians.
In January 2006, an alleged CIA missile strike in Bajaur killed 18 people, officials said.
Tribal militants have been blamed for a series of recent suicide bombings and other attacks in Pakistan.
The elders were driving in a car through the Charmangh area, about 20km (12 miles) east of Khar, when the explosion occurred.
"The two men died instantly while their third colleague sustained injuries and has been hospitalised," a local government official told Reuters news agency.
A local security official said the dead men had been working with the government on ways of controlling militant activity, the Associated Press news agency reports.
Tensions in the north-west rose in January after the military attacked a suspected militant training camp in the troubled South Waziristan tribal area.
At least eight people were killed. Locals say they were civilians, while the military disputes this.
Pro-Taleban militants in South Waziristan threatened revenge.