Kasab was hanged this morning at Pune's Yerwada jail after his mercy petition was rejected by the President on November 8.
Kasab was awarded death penalty by a sessions court in May 2010, which was upheld by the Bombay high court last year and the Supreme Court thereafter.
"By Kasab's conviction and death penalty, we have proved how the entire conspiracy was hatched in Pakistan. We have set an example that India will not tolerate such attacks and the accused will be brought to justice," Nikam said.
Nikam appeared for the prosecution in the sessions court and high court and assisted senior counsel Gopal Subramanium in the apex court.
Kasab and nine other Pakistani terrorists had landed in south Mumbai on November 26, 2008 after travelling from Karachi by sea and had gone on a shooting spree at various landmarks, killing 166 people, including foreigners.
While Kasab was captured alive, the other terrorists had been killed by security forces.