A rocket attack by NATO-lead foreign forces killed 52 civilians in southern Afghanistan, President Karzai's office said in a statement on Monday.
"52 civilians, including women and children, were martyred in an attack carried out by NATO and ISAF forces in Helmand province," the statement said.
Karzai strongly condemned the attack and called for international troops to increase their efforts to stop civilian causalities in their military operations.
The attack took place on Friday in Helmand's Sangin district, Daud Ahmadi, the provincial governor's spokesman, said.
Reports of civilian deaths and casualties caused by foreign troops are a major cause of friction between the Afghan president and his Western backers and often lead to street demonstrations.
In total, at least 1,074 civilians were killed and over 1,500 were injured in armed violence in the first half of 2010.