A head constable of Sashastra Seema Bal was on Wednesday killed in mysterious firing and another jawan was injured in Banihal area on the Jammu-Srinagar national highway, a senior police officer said.

The incident took place at around 7.15 pm and the police is investigating the cause of the firing, Senior Superintendent of Police, Ramban, Mohan Lal said.

"An SSB head constable suffered a fatal casualty in the brief firing while another jawan lost his jaw bone due to an attack by some blunt object," Lal said.

The deceased received one gun shot and his body was taken to the hospital for post-mortem, officials said, adding the injured jawan was also evacuated to a hospital for treatment.

"It is premature to say anything about the incident right now. We are ascertaining the details," the SSP said while not ruling out either a militant attack or fratricide.

He, however, said there was no retaliation from the SSB personnel to the firing.

The jawans were manning a post outside an 8.5 km-long under-construction tunnel connecting Banihal town of Ramban district in Jammu province with Kulgam district's Qazigund, the gateway to the Kashmir valley.