Ajmal Kasab, who had constantly denied the charges, stood up during his trial at a special court set up to try him and addressed the judge saying: "Sir, I plead guilty to my crime,"
A total of 166 people were killed in the rampage by 10 gunmen in Mumbai, India's financial capital, that began on November 26. It ended three days later with troops storming the Taj Mahal Hotel where some of the killers were hiding.
The confession appeared to take Judge M.L. Tahiliyani by surprise and he called lawyers from both sides to discuss its significance.
The confession will be a big boost to India's claims that terror groups in Pakistan were behind the attack, which severely strained relations between the two nuclear-armed archrivals.
In his lengthy statement, Kasab gave details of his group's journey from Pakistan on a boat, their subsequent landing in Mumbai and the bloody rampage that followed.
Public prosecutor Ujjwal Nikam said, "everybody in the court was shocked the moment he said he accepts his crime. It was unexpected."
"We are minutely assessing what he admitted in court," he said.
But Harish Salve, a senior Supreme Court lawyer, said it is not clear if Kasab confessed voluntarily.
"I am sorry to play the party spoiler. But I hope he doesn't come the day after and give it another twist," he said.
The developments came days after Pakistan gave a dossier to India with details of its investigations into the terror groups which New Delhi claims were responsible.
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