Raising slogans and holding placards, the supporters gathered opposite the main gate of the prime minister's residence, in an area which has been earmarked for mediapersons.
Many wearing Gandhi caps with "I am Anna" and holding placards in favour of Jan Lokpal Bill they shouted anti-government slogans.
Police had to forcibly evict them from the spot.
"We have detained around 40 people," a police officer at the Tughlak Road police station told IANS.
The all-party meet, which began around 3.30 p.m. has been called in a bid to chalk out the final draft of the Lokpal Bill.
Hazare's fast at the Ramlila Maidan to demand a strong anti-graft law entered its ninth day Wednesday.
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