Seven children were killed in a US-led coalition air strike on Sunday against a suspected al-Qaeda hideout in eastern Afghanistan, the coalition has said.
The US military says it did not know children were inside
It said a number of militants were also killed in the raid in Paktika province.
The children are believed to have been students at a madrassa, or Islamic school, at the targeted compound.
In the southern Uruzgan province, more than 100 people, including some 60 civilians, died in fighting over the past three days, Afghan officials said.
They said some 100 civilians were also injured as suspected Taleban militants and the Nato-led Isaf force fought fierce battles in Uruzgan's Chora district.
A Nato soldier from the Netherlands was killed in the fighting, the Isaf said.
President Hamid Karzai's spokesman condemned the Paktika air raid.
"The president was very unhappy, very sad when he heard about the incident," the spokesman, Karim Rahimi, told the BBC.
He renewed President Karzai's call for international forces to work more closely with the Afghan military.
Paktika's governor, Mohammad Akram Khpalwak, said he had been to the area to ask for forgiveness from local people and had ordered an investigation.
Earlier, a coalition statement said the air raid followed "credible intelligence" that al-Qaeda militants had taken shelter at the complex.
It said the compound in Zarghun Shah in Paktika province, about 120 miles (180km) south of the capital, Kabul, also contained a mosque and a madrassa.
The statement said that residents of the targeted compound reported that militants had been at the camp all day.
"This is another example of al-Qaeda using the protective status of a mosque, as well as innocent civilians, to shield themselves," coalition spokesman Major Chris Belcher said.
"We are saddened by the innocent lives that were lost as a result of militants' cowardice."
The coalition later said it did not believe any children were in or around the compound during the day.
It said other children who survived the air strike alleged that the seven children who died were held inside the building all day and beaten and pushed away from the door if they tried to go outside.
The BBC's Charles Haviland in Kabul says foreign forces in Afghanistan constantly accuse militants of using civilians as human shields.
There is, however, anger at the rising number of civilians killed in such foreign-led strikes, and President Hamid Karzai has repeatedly asked the coalition and Nato-led forces to try to minimise such casualties, he says.
The fact that the coalition issued this statement quite rapidly suggests it is expecting a negative reaction, our correspondent says.
Hours before the Paktika raid, a devastating bomb attack on an Afghan police bus in Kabul killed 35 people and injured more than 30 others.
The attack is thought to be the most devastating bomb attack in the capital since the Taleban were ousted in 2001.
Police said a number of civilians were also among those killed in the rush-hour attack close to police headquarters in the city centre.
Five foreigners were wounded in the attack.
The BBC's world affairs editor, John Simpson, says such an attack is disturbingly new on the streets of Kabul and the tactics appear to have been borrowed directly from Iraq.