Roadside bombs planted by Taliban fighters are a frequent cause of casualties in Afghanistan [Reuters]

Eleven members of an Afghan family have been killed by a roadside bomb in Zabul, a province in southern Afghanistan, officials say.

Roadside bombs planted by Taliban-led fighters, who have been waging an uprising against foreign forces for nearly 10 years, are a frequent cause of casualties among civilians in Afghanistan.

"Eleven civilians were killed after an IED hit their vehicle today at 7:50am," Mohammad Jaan Rasulyar, the deputy provincial governor of Zabul, told the AFP news agency on Saturday, referring to an improvised explosive device.

"They were en route to Ghazni province from Pakistan through Zabul's border area."

He said the group - five men, four women and two children - were all members of the same family and were thought to be Afghan refugees returning from Pakistan.

The attack in Zabul elicited a strong condemnation from Hamid Karzai, the Afghan president.

"The blood of the innocent people will not go unpunished," he said in a statement. "These terrorists will be brought to justice for their actions."

On Friday, another roadside bomb in the Khash Rod district of western Nimroz province killed 13 Afghan civilians, including children, and wounded 33.

The UN says 2,777 civilians people were killed last year, the highest total since the war started in 2001.

The UN also said last month that the number of security incidents in Afghanistan this year since March was 51 per cent higher than in the same period last year.

The Taliban's spring offensive - self described as Operation Badr- has seen a surge in violence in the past couple of months with attacks launched throughout the country. Civilians constitute most of the casualties in these attacks.

May was the deadliest month for civilians in Afghanistan since the UN began compiling statistics of casualties four years ago.

Source: Agencies