The incident took place on Tuesday in Marjah in Afghanistan's Helmand province, Peter Cook, spokesman for the US Defence Department said, adding that a number of Afghan forces were also injured, Xinhua news agency reported.
Two Medevac helicopters were sent to provide assistance. One was waived off after taking fire and returned safely to its base, and the second landed safely but sustained damage to its rotor blades after it apparently struck a wall, Cook said.
The spokesman said a fight is still going on in the immediate surroundings.
The US-backed forces have been fighting to suppress the Taliban in Marjah for weeks.
"The situation in Helmand and throughout Afghanistan remains challenging," Cook said.
"But we are confident that the Afghan national security and defense forces are continuing to develop the capabilities and capacity to secure the country against a persistent insurgent threat."