Three districts of Jalpaiguri, Darjeeling and Cooch Behar have already been placed on high alert and additional personnel have been deployed there, sources said.

In Kolkata, the police have increased surveillance in places like malls, metro stations, government offices and the Victoria Memorial.

“We will be basically monitoring places which are major entry and exit points like New Jalpaiguri, Howrah and Sealdah railway stations. We will be conducting random check of train coaches. Besides, bomb disposal squad will be deployed at important stations,” said Raj Kanojia, IG law and order. He added that long distance bus terminals will be monitored and buses will be checked.