A deadly car bomb has hit a hospital in Afghanistan's eastern Logar province.
There is confusion about the number of casualties, with officials saying between 20 and 60 people have died.
The hospital building was destroyed and people buried under rubble. Casualties included women, children and elderly.
The Afghan health ministry said the attack in Azra district was unprecedented. Officials blamed the Taliban, but a Taliban spokesman said they did not target civilians.
The blast was caused by "someone with an agenda", he said.
'Burning people'
An earlier suicide attack in Kunduz province killed 10 people the same day. (Photo: Sky News)
The BBC's Bilal Sarwary in Kabul says the Taliban is always careful to distance itself from major attacks with large numbers of civilian casualties.
Earlier the health ministry said 60 people had died in Saturday's attack, but some officials have since lowered that figure.
Authorities in Logar province said the death toll was 45, though officials in Kabul said it could be between 20 and 25.
An intelligence official said the hospital may not have been the intended target, but that the suicide bomber detonated the device when police gave chase to his car.
A large number of people had been gathering at the clinic, for weekly treatment, many of them women, children and elderly people, said provincial official Din Mohammad Darwaish.
Doctors and nurses were also said to be among the dead.
A man who lives near the hospital, Abdul Rahman, told AFP news agency he lost seven relatives in the blast.
"I was at home, then I heard a big explosion," he said. "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."
Soldiers have been sent to the scene to try to pull out those that are trapped.
A member of the Logar provincial council told the BBC: ''It is one of the saddest days. I have lost young, old, women, men - it is no less than a doomsday.
"The government and its intelligence agencies should have been able to prevent this. To the enemies of the people and Islam, I say, what do you get from a bloodbath like this? Almost every house, every family is grieving."
Our correspondent says there has never been an attack on a hospital in Afghanistan on this scale, although last month a suicide bomber attacked the main military hospital in Kabul, killing six people.
He says that members of the local community have recently joined the Afghan police, and that insurgents have warned people against doing so.
There is almost no central government control over Azra, which is close to the Pakistan border, and insurgents and smugglers are well-established there, he adds.
On Friday 10 people were killed and 24 injured by a bicycle bomb in northern Kunduz province.
Two days earlier, US President Barack Obama announced a partial troop pullout from Afghanistan.
He said 33,000 troops would leave this year, with the remaining 68,000 departing by 2013.
But there are concerns among the top US military that the withdrawal could endanger security gains.
A UN report earlier this month indicated a recent rise in civilian casualties.
It said May was the deadliest month for civilians in Afghanistan since records began in 2007, with 368 killed.
It added that 2,777 civilians died in 2010, making it the worst year, with three-quarters of the deaths blamed on insurgents.