Nine people died in the collision in Helmand province
All those who died were on board the helicopters, officials say.
The incident early on Wednesday in Nawa district was apparently caused by technical issues.
The area has seen fierce clashes in recent days between the Taliban and Afghan government forces, supported by US airstrikes.
The insurgents have been fighting their way to the outskirts of the nearby city of Lashkar Gah where they have already taken control of one district.
The United Nations in Afghanistan says more than 35,000 people have been forced to flee their homes in Helmand.
It’s the most serious and sustained attack by the Taliban since peace negotiations began last month in Qatar, the BBC’s Secunder Kermani says.
So far discussions have been bogged down in attempts to finalise a set of rules and procedures governing the talks – and negotiators are yet to broach the broader issues of a ceasefire and possible power sharing arrangement.
Large parts of Helmand and neighbouring Kandahar remain without electricity after the Taliban attacked a power substation on Monday.
A number of telecommunication networks have also been shut down.
Of about 5,000 families estimated to have been displaced, some are reported to have sought refuge in homes and properties in neighbouring areas.
News Source : BBC World