Several 'squatters' carrying Trinamul flags stopped a police contingent from earmarking government land in Chowbaga, about a kilometre off Ruby hospital, on Wednesday.
The 60-member team with two assistant commissioners had accompanied land and civic officials to the spot in the afternoon.
But no sooner had the first bamboo shaft been fixed to earmark a portion of the land, women from a slum on the plot came running and toppled the guard rails and pushed the police away.
The estimated value of the 145-acre plot near the Urbana housing project is almost Rs 4,350 crore.
"Mamata Banerjee has compensated farmers in Singur. How come her own police are here to take away our land?" asked Bimala Naskar, 55, who works as a maid in nearby housing complexes.
"We want her to come here and listen to us," she said. Naskar claimed she had a bigha of land in the area.
Some among the protesters produced barga certificates, issued by the Left government in the 1987, to justify their claim on the land.
But a legal expert said the document gave them only the permission to till land. They cannot claim ownership, he said.
Naskar, armed with a stick, was part of a 50-woman brigade who ensured the cops retreated for the third day since the operation to earmark government land began last Friday.
When Metro asked the cops why they were not taking any action despite such heavy police presence, an officer said: "Our seniors have instructed us not to use force."
The Chowbaga land belonged to a zamindar. The government had taken over the land after the zamindari system had been abolished.
The original owners moved court in the 1970s against the government move.
In March this year, a division bench of Calcutta High Court ruled in favour of the government.
Now, the occupants of the plot want compensation if the government wants to take over the land.
One of the protesters, Bappa Dalui, who works as civic contractor, said: "Farmers should get five cottahs of land as well as appropriate compensation for the rest of their land that the government takes over."
Of the 11 people who claim to be the current landowners, Uday Shankar Roy, a descendant of the original zamindar Sidhar Chandra Roy, was at the site on Wednesday.
He told the protesters that he would continue the legal battle with the government to get back possession of the land.