New Delhi: Security forces went on high alert across the country on the eve of Independence Day in view of threats by militant outfits to disrupt the celebrations even as six bus passengers were killed in a blast triggered by militants in Manipur.

In the capital, where Prime Minister Atal Behari Vajpayee will unfurl the national flag and address the nation from the ramparts of the Red Fort on August 15, police and paramilitary forces have been deployed in strength.

Sharp-shooters took up positions on high-rise buildings in the vicinity of the historic venue and the entire area has been declared "out of bounds" for the public.

Air traffic in Delhi and some of its adjoining areas will be suspended for six hours from 04:00 hours on August 15 and two helicopters will maintain an aerial surveillance to prevent any terror strike like the September 11, 2001 attack in US.

Extra security measures were being taken in the North East especially in Imphal where militants struck in the wee hours of August 14 killing six bus passengers and injuring 15 others.

In Jammu and Kashmir, intelligence agencies have intercepted wireless messages of militants suggesting suicide attack in Jammu region. A multi-tier security ring had been thrown around the city of temples with Army assisting the civilian administration.

PTI