"We have heard of heavy casualties too and have sent a team to investigate this," he said.
At least 20 wounded civilians had been brought to a main hospital in Lashkar Gah, the provincial capital of Helmand province, he said.
In the hospital, Shokhi Khan, a relative of one of the wounded, said several hundred civilians were killed or wounded in the strikes.
He said people had gathered for picnics and to go to a shrine in Baghran district north of Lashkar Gah on Thursday when the raids started.
Haji Hakim Jan, 27, said he lost four of his brothers in the attack.
|"During a sizeable meeting of senior Taliban commanders, coalition forces employed precision guided munitions on their location" |
US military statement
"I had another brother of mine and an eight-year-old sister wounded in the bombing," he said
The US military said in a statement that the air raid had been conducted against two "notorious Taliban commanders" holding a meeting in a remote area of the Baghran district.
"During a sizeable meeting of senior Taliban commanders, coalition forces employed precision guided munitions on their location after ensuring there were no innocent Afghans in the surrounding area," a statement said.
It added that the fate of the pair was unknown.
The Nato-led International Security Assistance Force which works alongside the US-led coalition said the air strike was only called after multiple sources confirmed that several Taliban leaders and their followers were at the site.
Some residents and an official said the bombings occurred as a large crowd of people had gathered to watch an execution being carried out by the Taliban movement.
The Afghan defence ministry said several Taliban leaders including Mansour Dadullah, the group's senior commander in the south, were attending the execution of men accused of spying for the government.
A purported Taliban spokesman denied there had been a public execution and said those killed were all civilians attending a ceremony at a shrine.
There was no independent verification of the reported accounts from either side.
More than 350 civilians have been killed in operations by foreign forces this year in Afghanistan, according to government officials and aid workers.