Security has been tightened across Punjab, Haryana and Chandigarh ahead of Independence Day celebrations. Security has been beefed up at the venues where the dignitaries will unfurl the Tricolour and at important railway stations including Chandigarh, Panipat, Ambala, Ludhiana and Jalandhar, besides key inter-state bus terminals and other vital installations, officials said on Wednesday. Police have asked operators of guest houses, cyber cafes, telephone booths and taxi services to keep a watch on their customers and report any suspicious persons. Police and other security personnel have intensified checking of vehicles in the two states and Chandigarh, where several 'nakas' have been set up. Barricading and checking have also been intensified at the inter-state borders.