The sources said 150 police personnel were deployed in a 24-hour period in shifts at the US embassy, the American School and American Centre in New Delhi.
As many as 50 police personnel were deployed at any given time in Chanakyapuri near the embassy.
Two police vehicles were permanently stationed along various roads near the embassy, the sources said.
There was 24x7 patrolling to ensure smooth flow of traffic, and measures such as speed breakers were also in place.
Security barriers outside the US embassy were removed last month as part of a response by India after the arrest and strip search of Devyani Khobragade, India's deputy consul general in New York, that led to outrage in India.
--IANS (Posted on 02-01-2014)