ew Delhi, Aug 11 - Security has been beefed up especially in New Delhi, Kolkata and Hyderabad after the home ministry warned police in three cities to raise their levels of preparedness to face up any terror attack in the run-up to the Independence Day Saturday.

Senior ministry officials told IANS that advisories have 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 ministry has asked police to strengthen security in market places, cinema halls, bus and railway stations and iconic buildings in the three cities.

The US government, in a fresh security alert to its citizens in India, also haswarned 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 Aug 15 Independence Day celebrations) 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,' it added.

Delhi Police have begun making unprecedented and elaborate security arrangements across the national capital to ward off any untoward incident.

'We will have in place an unparalleled ground-to-air security apparatus for the Independence Day celebrations. Security will be tighter and flawless in view of certain threats,' said a senior security official.