Ujwal Nikam, the special public prosecutor in the high-voltage case, admitted he was 'surprised' at the 'unexpected' confession for the first time in the court hailing it as a big victory for the prosecution.
He said Kasab may have realised that the 'cat is out of the bag' after 134 witnesses gave evidence against him since the trial began in April.
But another criminal lawyer Satish Manishinde counselled caution saying it should be known whether the 'belated' confession was voluntary and whether he was coerced or he got any instructions, even though there was clinching evidence to his involvement.
The action of the Pakistani national pleading guilty on the 65th day of his trial in the high security Arthur road prison left those in the special court shocked.
And Judge M L Tahiliyani, who was apparently taken aback, called lawyers from both sides to figure out the significance of Kasab's statement.
"We are surprised that Kasab has abruptly taken this stand (of confessing to involvement in 26/11 attacks)," said Nikam.
"Everybody in the court was shocked the moment he said he accepts his crime. It was unexpected," he said, adding," We are minutely assessing what he admitted in court," he said.
Senior Supreme Court lawyer Harish Salve, said it is not clear if Kasab confessed voluntarily.
"I hope it is not a ploy and he doesn't come the day after and give it another twist," he said.
Kasab's lawyer Abbas Kazmi was reported to be unaware that his client was going to plead guilty to all the charges levelled against him.
It was not immediately clear what prompted Kasab to make the statement after consistently denying he was guilty over the last 65 days of the trial.
Asked whether there was police pressure on Kasab to admit his crine, Maharashtra Chief Minister Ashok Chavan replied in the negative. "No, there is no question of police pressuring anybody," he added.
He however said the trial should be completed quickly and all those involved in the attacks should be hanged.
"I believe that the entire conspiracy was hatched by these Pakistani nationals and it was only a formality," he said.
Nikam told mediapersons that Kasab had "stood up and informed the court that he was willing to confess."
In Manishinde's view, the confession was a 'tactical' move by Kasab and his team.
"It is obvious that he has got enough instructions to what he has done today," he added.
Another criminal lawyer Majid Memom said the court should ascertain whether Kasab's admission was voluntary or involuntary and whether pressure was brought to play.
The day's proceedings were due to start from eye-witness evidence from a police officer who witnessed the shootings.