A remote-controlled roadside bomb tore through a vehicle transporting Afghan aid workers in northern Afghanistan on Tuesday and killed three, police and the humanitarian group said.
The group was travelling to a district near the border with Uzbekistan and Turkmenistan to select families to benefit from a shelter project, said a Development and Humanitarian Services for Afghanistan (DHSA) board member.
"Along the way, their vehicle was struck by a remote-controlled bomb and they were all killed," Shafiqullah Wardak told AFP. "They were torn into pieces by this barbaric act."
The dead were a driver and two employees for the programme which provides shelter to families that have returned from exile, Wardak said.
They were killed in the northern province of Jawzjan which has seen little of the Taliban-led insurgency gaining pace in the south and east of Afghanistan, although officials have said the violence is spreading in the north.
The UN refugee agency said it had been working with DHSA and it regretted the loss of life.
"DHSA is a long-time implementing partner of UNHCR and provides shelter to returning refugees," it said in a statement.
Jawzjan police chief Mohammad Ibrahim said the Taliban were responsible for the attack. A representative for the insurgent group however denied involvement.
Aid groups working in Afghanistan, one of the poorest countries in the world, have come under attack as the insurgency has gained pace with criminal groups also able to operate.
Thirty-one aid workers were killed in attacks last year, said Mohammad Hashim Mayar, deputy director of an umbrella body for nearly 100 Afghan and international non-governmental organisations.
This compared to 17 killed in 2007, he told AFP.
"It is not only the Taliban, there are criminals as well who attack for personal benefit, not group benefit," said Mayar, from the Agency Coordinating Body for Afghan Relief.
Aid groups were often protected by the communities that they help, he said. "But killings sometimes happen on their way to areas where they work and there the community cannot help," he said.