The airstrike was carried out late on Sunday night targeting the Mullah Manan and his fighters in the vicinity of Marjah district.
Provincial security chief Gen. Agha Noor Kentoz said Muallah Manan was initially injured in the attack and later died of his wounds.
He said the airstrike was carried out as part of Khanjar operations which were launched six days ago in Marjah to suppress the insurgency activities of the Taliban militants.
The Taliban militants group has not commented regarding the report so far.
This comes as at least 8 militants were killed during an attack on the Taliban prison in Marjah district earlier.
The Ministry of Defense said 7 militants were also arrested an Improvised Explosive Device (IED) manufacturing factory was destroyed along with a vehicle and two motorcycles belonging to the militants.
At least 19 hostages were also released from the prison belonging to the Taliban militants during the raid, MoD added.