At least 12 Afghan policemen have been killed by a bomb dropped from a US-led coalition aircraft in south-east Afghanistan, officials say.
Afghan President Hamid Karzai condemned the raid, in Paktika province.
But US officials said they were confident that the two trucks they hit were the same ones which had been used in an attack on coalition forces.
US and Nato forces are fighting the Taleban, mainly in the south and east.
The incident came on a day when gunmen kidnapped at least 15 people, including a doctor and nurses, in the southern province of Kandahar. One report said they were later freed.
Investigation
Deputy chief of border police General Abdul Rahman said the coalition aircraft mistakenly dropped a bomb on a two-vehicle border police patrol.
The bodies of the dead had been brought back to Paktika's capital, Sharan, he said.
Mr Karzai said: "I am extremely saddened by this tragic incident and I want an immediate investigation to find out what exactly happened.
"I have repeatedly asked the coalition forces to take maximum caution while carrying out operations and I want that incidents like this must not be repeated."
US Lt Col Paul Fitzpatrick said the attack followed a clash with extremists in the Waza Khwa district, in which one Afghan soldier was killed and a coalition vehicle damaged.
"We are aware that local officials have stated that Afghan border police were attacked and killed by coalition aircraft, and we are investigating that report," he said.
A second Afghan official said two people were also injured in the incident.
Earlier in the day, parliament approved Amrullah Salehi as the country's new head of intelligence, amid criticism that intelligence being passed by Afghan authorities to US forces was inaccurate.