Security agencies Thursday carried out a mock drill at the Reserve Bank of India's (RBI) headquarters here, which involved a helicopter hovering over the 25-storey building in south Mumbai. A video shot from the street below shows a helicopter coming over the RBI building's terrace and a few security men slithering down.

As part of the mock drill, the security establishment created a "hostage situation" where people had to be evacuated from a particular floor in the RBI building, sources said. The entire operation, involving multiple agencies, was planned to the last detail, they said.