An alert was sounded in the National Capital Region after a suspicious balloon was noticed in Gurgaon on Wednesday afternoon, police said.Informed sources said the Delhi Police issued the alert after Gurgaon Police first spotted the balloon in its area. Indian Air Force and Delhi's Indira Gandhi International Airport authorities were also alerted.The development comes a day after the IAF said it shot down "an unidentified balloon" in Barmer district of Rajasthan.Gurgaon Commissioner of Police Navdeep Singh Virk said: "At about 3.15 p.m., patrol guards at the IAF Station on the Gurgaon-Faridabad road reported the sighting of an unidentified red-and-white balloon of about one-metre diameter, flying 1-1.5 km high towards Aya Nagar in Delhi from the Gurgaon-Faridabad Road side. "The Gurgaon police control room alerted its counterparts in Delhi and Faridabad. No balloon has been recovered as yet but further enquiries are in progress."