The 74-year-old thespian on Tuesday night shared two photographs of himself performing an aarti on a beach for a scene in the film.
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"In prayer for Sarkar 3' and the aarti for Ganesh, which I have sung," Amitabh tweeted.
The scene was shot at the Juhu beach here, and Big B said the serious look for the scene -- as seen in the photographs -- is deliberate.
"In prayer for the aarti for 'Sarkar 3' on the beach of the Arabian Sea off Juhu and behind one of the prominent hotels of the area. The sinister serious looks even for the Ganesh aarti, is deliberate and pertinent for the scene," he wrote on his blog.
"The aarti has been sung by me. No, it is not the same one I did for Siddhivinak Temple, it is differently placed, more pertinent to the events of the story of the film," he added.
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The film is the third instalment of the popular crime movie "Sarkar".
The cine icon had played an integral part in the first two instalments of the film.
"Sarkar", which released in 2005, is set up in the world of Indian politics. Its sequel "Sarkar Raj" hit the screens in 2008.
"Sarkar 3" will see Amitabh reprising his role as Subhash Nagre. The film will also features Rohini Hattangadi, Jackie Shroff, Manoj Bajpayee, Ronit Roy, Bharat Dabholkar and Yami Gautam.
IANS