A huge car bomb at a hospital on Saturday killed 60 in Afghanistan’s worst attack for three years, days after US President Barack Obama said 10,000 US forces would leave the country in 2011.

The brazen suicide attack in Logar province, about 75 kilometres south of the capital Kabul, killed women and children and also wounded 120.

As an eyewitness described horrific scenes of victims on fire following the blast in the usually safe Azra district, officials described the attack as “unprecedented” in the near-decade-long Afghan war.

“Sixty of our countrymen including children, women, youths and men. Have been martyred and 120 others including health workers have been injured,” the ministry of public health said in a statement.

“This inhumane act is unprecedented in the history of the conflict in our country and targeted a place where wounds are healed and patients receive treatment.”

Din Mohammad Darwaish, the Logar provincial spokesman, said the blast — which took place close to Afghanistan’s border with Pakistan — was a suicide car bombing.

The Taliban denied it was behind the attack, which completely destroyed the building. Spokesman Zabihullah Mujahid said: “We condemn this attack on a hospital. Whoever has done this wants to defame the Taliban.”

One man who lives near the hospital, Abdul Rahman, told AFP that he lost seven relatives in the explosion.

“Seven members of my family including three women and two children went to that hospital this morning,” he said, through tears.

“I was at home, then I heard a big explosion. When I rushed to the site, I saw many dead and injured people.

“Many of them were burning, on fire. There were body parts everywhere. My family is dead, I can’t find them, they are under the rubble.”

The huge blast caused the highest death toll in Afghanistan since a July 2008 car bomb attack on the Indian embassy in Kabul killed more than 60 people.

It came at the end of a week when Obama announced that 33,000 US forces would leave Afghanistan by the end of next summer.

All foreign combat forces are due to pull out of the country by the end of 2014. There are currently up to 150,000 foreign forces in Afghanistan, including about 99,000 from the US.

Some analysts fear that Afghan security forces may struggle to contain the insurgency, which has hit record levels of violence, as withdrawals begin.

Afghan President Hamid Karzai condemned the attack as “savage and ignorant” in a statement released by his office.

It came as Karzai told a counterterrorism summit in Tehran that militancy was on the rise in both his country and the region.

"Not only has Afghanistan not yet achieved peace and security but terrorism is expanding and threatening more than ever Afghanistan and the region," he told the opening session.

The two-day summit is being attended by the heads of state of six regional countries, including Afghan neighbours Iran and Pakistan.

The blast in Logar is the second major attack in Afghanistan in two days.

On Friday, 10 people were killed by a bicycle bomb which went off in a busy bazaar in Khad Abad district of the northern province of Kunduz.

Militants in Afghanistan frequently target the Afghan police and other government employees as well as foreign forces in their near decade-long insurgency.

But civilians are the biggest casualties in the war, with 2,777 killed last year, according to the United Nations.