Vellore: A 52-year-old retired military officer from Keelvallam near Vellore has been arrested for spying and leaking defence secrets to a woman on WhatsApp in Vellore.The accused, identified as Babu, served in the Army for 28 years before retiring a year ago as Captain. He was detained and interrogated by central intelligence agencies for two days before being handed over to police, who arrested him on Sunday. He was booked on multiple counts including spying and leaking classified information, posing a threat to sovereignty, unity and integrity of India.According to sources, Babu was approached by an unidentified woman via WhatsApp about year ago. The two grew close, frequently engaging in detailed conversations and video calls. Under the pretext of working on a DRDO (Defence Research and Development Organisation) project, the woman sought sensitive details concerning military from him, police said.Investigators said Babu not only shared information that he was aware of, but also contacted former colleagues, serving as well as retired, to gather information which was then shared with the woman. Details about the woman, said to be from UP, were not immediately available.Acting on a tip off, central intelligence operatives picked up Babu from his residence, and brought him to the Vellore taluk police station. Following two days of intensive joint interrogation, he was formally handed over to local police.Police booked him under section 152 of BNS and sections 3 (1) (c) and 5 (1) (a) of the Official Secrets Act, 1923.Police said further probe involving National Investigation Agency (NIA) and other central intelligence agencies are likely in the coming days.