They said watch towers have been put up at strategic points while footage of traffic signals was also being monitored
Railways also have tightened security at all stations in the city and additional personnel have been deployed in Chennai Central, Egmore and Tambaram stations in particular, a senior RPF official said.
Temporary bunkers have been put in important stations and CCTV footage is being closely monitored, they said.
He denied media reports that RMS parcel service has been suspended, saying it has only been restricted. "Anything suspicious will be stopped and checked throughly."
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One foot metal detector has been issued to all teams deployed to check luggage, he said, adding bomb squads have been deployed for round-the-clock anti sabotage operations.
At the airport,screening of visitors would be in place in addition to checking of baggage and passengers,CISF sources said.
Movement of people in bus terminals, malls, shopping complexes, busy junctions and narrow lanes are also being watched, police said.
A Coimbatore report said about 3,500 police personnel, including paramilitary forces, have been deployed at strategic places, including major government installations, places of worship, railway stations, bus stands and areas were large numbers of people gather and also in rural limits.