Unidentified gunmen have shot dead four officials from Pakistan's secretive ISI intelligence agency in a tribal region bordering Afghanistan, officials say.
Two others were wounded in the attack in the Rashkai area of Bajaur agency, local authorities said.
Initial reports say the officials were travelling to the main town of Khar when they were ambushed.
No group has said it carried out the attack, a day after tribes vowed not to shelter al-Qaeda or Taleban militants.
Monday's deal in Bajaur with the government followed other similar controversial accords elsewhere in the tribal region, which critics say have encouraged a Taleban safe haven on the border.
News of Tuesday's ambush is still emerging and details surrounding it are sketchy.
The BBC's Haroon Rashid in Peshawar says it took place near where a suspected top al-Qaeda leader Abu Marwan was killed last year.
Officials said the gunmen were wearing masks and riding on a motorbike. Hand grenades were also used in the attack, they said.
The dead included an Inter-Services Intelligence (ISI) assistant director, Mohammad Sadiq, alias Major Hamza.
"Masked men riding on a motorbike opened fire on the vehicle when the ISI officials were coming to Bajaur tribal district from Peshawar," local intelligence official Moaz Khan told the AFP news agency.
There was anger after a madrassah was bombed last October
The wounded were taken to hospital in Khar, where they are said to be in a critical condition.
It is unclear who might have carried out Tuesday's attack. There have been after a string of attacks by suspected pro-Taleban militants in the troubled border region in recent months.
Bajaur was the scene of two major attacks against suspected militants last year, which caused great anger among locals and people elsewhere in Pakistan.
In January, at least 13 people were killed when American forces struck three compounds, apparently after reports that al-Qaeda number two Ayman al-Zawahri was in the area.
An air raid by Pakistani forces on a religious school in October left more then 80 people dead.
The officials did not say what the ISI officials were doing in the area.
The notorious ISI is a central organ of Pakistan's military machine which has played a major - often dominant - role in the country's often turbulent politics.
Critics say it runs "a state within a state", subverts elected governments, supports the Taleban and is even involved in drug smuggling.
Pakistan's government denies the allegations.