Five farmers were killed by an air strike from Western forces, Afghan police said Thursday.

The farmers were loading cucumbers into a taxi in the rural Zhari district near Kandahar city when a military helicopter fired on them, said district police Chief Niaz Mohammad Sarhadi.

Sarhadi alleged the strike was conducted by U.S. forces in Afghanistan.

Lt.-Cmdr. Christine Sidenstricker said the U.S. military believes the air strike hit a group of militants loading munitions into a van.

Officials will review footage from the Apache helicopter to determine what happened, Sidenstricker said.

Villagers in southern Afghanistan expressed outrage on Wednesday after a Western air strike killed three young boys and a man.

The U.S. military maintained it had killed four insurgents on motorcycles in Kandahar province and could not confirm any civilian deaths.

The deaths of civilians at the hands of foreign troops have caused deep resentment among Afghan people. President Hamid Karzai has repeatedly called on foreign troops to halt air strikes and raids in Afghan villages.

Newly appointed NATO Secretary General Anders Fogh Rasmussen acknowledged the issue of civilian casualties is a sensitive one.

"We have seen a number of civilian casualties," Rasmussen said after arriving in Kabul Wednesday to meet with Karzai. "I strongly regret that, but I can assure you that it is our clear intention to do everything possible to reduce the number of civilian casualties to an absolute minimum."

With files from The Associated Press