The young sub-inspector T Alwyn, who had joined the force only last year, was regulating vehicles at Podukulam when he was attcked by the youths, police said.
He had asked the youths to take another route to proceed to Sivaganga District for the 'guru pooja' of the two brothers, 18th century rulers of Sivaganga who fought against the British.
Infuriated over being diverted, the youths attacked the SI with sharp weapons. Two other police personnel who were at the spot were also injured in the attack, police said.
The gang members had also pushed down a DSP from his jeep and escaped in it, abandoning their vehicle.
Alwyn, survived by wife and two toddlers, was rushed to the Government Rajaji Hospital here where he succumbed.
