In the wake of the RDX haul in Haryana,the Centre has advised authorities in four metros besides Hyderabad and Bangalore to remain on high alert as terrorists may try to strike during the festival season. Acting on intelligence inputs,the Centre asked authorities in Delhi,Mumbai,Kolkata,Chennai,Hyderabad and Bangalore to remain on high alert to foil any possible terrorist design to attack cities in the run up to and during Diwali and other festivals,sources said today. The Centre asked the police chiefs of these cities to intensify vigil and deploy additional forces in all sensitive locations,religious places,markets,airports,railway stations,bus terminals and other crowded places to ensure peace. Over 5 kilograms of RDX was recovered from a car outside the Ambala Cantonment railway station on Wednesday night by the police which claimed it had succeeded in foiling a terror strike,possibly in Delhi and plotted by terror outfits Lashkar-e-Toiba and Babbar Khalsa International. The explosives were recovered following inputs provided by intelligence agencies ten days ago that a consignment of such material was headed for a north Indian metro.