In view of the violence, polling has been stopped at five polling booths even as a contingent of police and BSF personnel have been rushed to the area.
Officials said a Border Security Force (BSF) platoon deployed in village Balapra and Harbhanga for poll security duties opened fire to save election officials and police personnel after a group of 40 people tried to capture a booth.
"A total of ten rounds have been fired. While one policeman has been killed another is seriously injured after they were attacked by the mob," a senior official said.
A BSF party positioned nearby immediately swung into action and ensured the retreat of the unidentified attackers.
Two INSAS rifles, of the killed and injured policeman, have also been looted.
Polling in underway in six Lok Sabha seats in Assam today.