NEW DELHI: On a day prime minister Narendra Modi would be addressing the nation for the first time on Independence Day, security agencies will be on their toes with intelligence inputs indicating that the al-Qaida and ISI are planning to target American establishments in the capital as well as carry out a 26/11-type attack on South Block, North Block and Central Secretariat.Security agencies have intercepted conversations which indicate that there was a high degree of threat to the twin power centres and Central Secretariat along with its Metro station.Police have been conveyed these inputs and, in turn, increased the security of these three places. Deployments and air defence system around Vijay Chowk have been upped as well.What has bothered Delhi Police most is that the security alert that Al Qaida chief Ayman al-Zawahiri has formed a crack team of three Pakistani operatives, who are experts in handling and making IEDs, to target the US embassy and other American establishments.While much is not known about the identity of these three terrorists, the sleuths have got to know that they have previously lived in India and also travelled to and from India and Pakistan.Agencies have accorded these inputs top priority and are trying to gather more information. At present, the special cell is grilling several American Center attack accused and LeT men in its custody.This, coupled with threat perception of the Prime Minister has led police to draw out an "unprecedented security arrangement" this Independence Day.Areas of Red Fort, South Block, North Block, Central Secretariat, Connaught Place, Tilak Marg, India Gate and Parliament Street areas will attract maximum security.There will be multi-layered security for Independence Day comprising the army, paramilitary and Delhi Police. Paramilitary troops have also been positioned at strategic locations in central Delhi.All areas have been sanitized and important junctions are being constantly monitored from the C4i (command room). snipers and SWAT teams of special cell positioned strategically.Around 15,000 security personnel have been deployed across the capital and security agencies have also intensified their anti-sabotage and anti-explosive checks to thwart any form of terrorist strikes, including vehicle bombs and fidayeen attacks.