Central intelligence agencies have alerted Kolkata police about the possibility of a terror attack in the city, especially in the port area, a senior official of Kolkata police said on Tuesday.
The warning is believed to have forced the withdrawal of two Indian Navy warships - INS Khukri and INS Sumitra - that had docked at Kolkata for Navy week celebrations.
A defence ministry statement, however, said they have been "withdrawn for undisclosed operational reasons."
The warships were scheduled to be anchored in Kolkata till Friday, and were to be opened to the public on Wednesday and Thursday.
Intelligence sources said the terror threat was issued after some intercepts suggested that there was a terror threat to the Kolkata port. The West Bengal government held a high-level security meeting with central agencies, the Army and the Navy and decided to sanitise the port. The dock complex in Haldia has also been put on alert.
The coast guard and other agencies have also been alerted.
"We have received inputs from central intelligence agencies that there might be a terror attack in Kolkata, especially in port area. We have increased security in the port area and have put the entire city under security blanket," a senior police officer said on condition of anonymity. Times Now reported, quoting sources, that al-Qaeda may be the terror group behind these attacks.
According to the input, terrorists might carry out an attack in the port area and may use small boats to carry out the strike, he added.