The Home Ministry has warned the police in three cities to raise their levels of preparedness to face up to any terror attack in the runup to Independence Day on Saturday.
Senior ministry officials told IANS that advisories had been sent to the police forces of New Delhi, Kolkata and Hyderabad to be alert, indicating that intelligence inputs had warned of possible attacks.
The Home Ministry has asked the police to strengthen security in market places, cinema halls, bus and railway stations and iconic buildings in the three cities.
Meanwhile the US government, in a fresh security alert to its citizens in India, has also warned of possible terrorist attacks in the country.
A message issued last week asked American nationals in India to "maintain a heightened situational awareness and a low profile".
"There is a continuing threat from terrorism throughout India and the upcoming series of major holidays (including the August 15 Independence Day celebration) could provide terrorist groups an opportunity or pretext to stage an attack," the advisory said.
"The November 2008 attacks in Mumbai provided a vivid reminder that luxury hotels are especially attractive targets for terrorist groups," the advisory added.
Home Minister P. Chidambaram has called an internal security meeting of all chief ministers Aug 17 to address the growing incidence of Maoist violence and formulate a counter-offensive against the rebels.