Two members of the South African National Defence Force have been airlifted to a military hospital in Pretoria following a helicopter crash in Zwartkop.

Best Care Ambulance Services spokesperson Xander Loubser said paramedics had received a call about a military helicopter that had crashed in a veld.

Xander said he didn't know yet what had caused the crash.

"When paramedics arrived on the scene, there were no ground injuries. The chopper crashed on the grass. Two members of the defence force were on board. The two sustained serious injuries.

"The members were treated on the scene, before they were airlifted by another military helicopter to a military hospital. Our paramedic escorted the second chopper to hospital," he said.