A senior police officer said the 28-year old jawan, identified as Ratheesh, allegedly molested the woman by sneaking into her house near the headquarters of the 83 battalion of the border guards while she was asleep yesterday.
He was thrashed by local people when the matter came to light. He was later taken to the hospital of the border force in a serious condition.
A BSF spokesman said full cooperation will be extended to the police in its investigation and action will be taken against the personnel for "sullying the image of the force."