Prime Minister Narendra Modi has accepted the resignation with "regret and expressed appreciation for Sandhu's outstanding service to the country in a career spanning over 40 years", an official statement said.
A career police officer, Sandhu was also the Secretary, National Security Council Secretariat.
Sandhu headed the Intelligence Bureau in 2010-12, and was highly regarded for his contribution to India's fight against terrorism.
Some in the security establishment described Sandhu as a successful clandestine operative and a brilliant analyst.
A career police officer, Sandhu was also the Secretary, National Security Council Secretariat.
Sandhu headed the Intelligence Bureau in 2010-12, and was highly regarded for his contribution to India's fight against terrorism.
Some in the security establishment described Sandhu as a successful clandestine operative and a brilliant analyst.