Kolkata and its port area may face a terror attack, according to a warning issued by central intelligence agencies amid which the Navy has withdrawn its two warships that were docked at the port here.

A senior Kolkata police official said that inputs have been received from central security agencies that there might be a terror attack in Kolkata, especially in the port area.

"We have beefed up security in the port area and have put the entire city under security blanket," he said.

Amidst this warning, Navy warships - INS Khukri and INS Sumitra - which had docked at the port last evening and was scheduled to be there till November 6 for public viewing as part of Naval Day celebration, made a sudden withdrawal on Tuesday.

Official sources in Delhi said the withdrawal was a precautionary measure.

However, when asked whether the withdrawal of the ships wa because of the terror alert, Defence CPRO Group Captain T K Singha said "no, it has nothing to do with any terror alert. The recall of ships is strictly due to operational reasons."

A Defence press statement issued in Kolkata said "the alacrity by which Indian warships are ready for operation at a short notice was demonstrated by the quick turnaround of the two visiting warships amply showcasing Indian Navy's prompt readiness as the two warships are set to sail out within hours of a recall to the sea for undisclosed 'operational reasons' on orders by Eastern Naval Command HQ, on Tuesday."

The Pentagon claims in its latest six-monthly report on the current situation in Afghanistan that Pakistan is using such proxies to counter the Indian armed forces as well as to hedge against the losing of power and control in Afghanistan.

Such relationships oppose Pakistan's commitment to support Afghan-led reconciliation and these groups continue to act as the primary source of contention between Afghan- Pakistan bilateral relations, claims the Pentagon report.

The Pentagon also mentioned an attack on the Indian consulate in Herat that took place three days ahead of the swearing-in ceremony of Indian Prime Minister Narendra Modi.

The fact that Modi is believed to be close to Hindu nationalist groups may have played into the timing of the attack, said the Pentagon.

However, welcoming the Pentagon report, External Affairs Ministry spokesman Syed Akbaruddin said that if the international community is acknowledging the fact that terrorism derives support from Pakistan, it is something that New Delhi welcomes.