"The informal directive came after Pakistani American Lashkar terrorist David Coleman Headley's confession that he recced several targets including Sena Bhavan," a party source said.
Many overseas students come to the Sena Bhavan to study the party and its functioning, the source said.
Headley may have come to the headquarters pretending to be one of them and recced the office. So as part of security measures, the decision was taken by senior leaders, the source said.
Headley had also told interrogators from the National Investigation Agency that he filmed the outer boundary of the prime minister's residence (7, Race Course Road in New Delhi) during his trip to the capital in March 2009.
He also disclosed how Pakistani intelligence agency the Inter Services Intelligence had been behind the 26/11 Mumbai terror attacks, and made plans for other terror strikes in Delhi, Pune, Goa and Pushkar.