The provincial governor’s spokesman Taliban Mangal confirmed the incident and said the blast took place during Friday prayers.
Mangal added that at least nine soldiers were killed and 22 others were wounded in the explosion.
The Defense Ministry Spokesman Jawid Ghafoor, meanwhile, said that helicopters were being sent to the province to transfer the wounded soldiers to hospitals.
According to Ghafoor, a delegation has been dispatched to Khost to probe the incident.
No individual or group has immediately claimed responsibility for the attack.