The serial blasts in Assam on Thursday led to an alert being sounded in neighbouring West Bengal districts that have common borders with that state.
"Special alert has been sounded in north Bengal districts of Jalpaiguri and Coochbehar, which have common borders with Assam," Inspector General of Police (Law and Order) Raj Kanojia told PTI in Kolkata.
In the metropolis, security was tightened in Sealdah, Howrah and Kolkata railway stations as also at Metro rail stations.
The police have been specifically asked to keep watch on shopping complexes, parking lots and markets.
Additional policemen were also deployed in public places.