The incident took place when the 51mm mortar fell short of its target at the forces' firing range in Kishangarh. The four personnel -- an inspector, a head constable and two constables -- suffered injuries due to the blast of the ammunition.
They were participating in a firing exercise.
Officials said the four men have been air evacuated to a hospital in Jodhpur, adding two of them have suffered critical injuries.
The BSF is deployed in Rajasthan as part of its task to guard the India-Pakistan International Border (IB).
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