25-year old Kasab was hanged at 7.30 am in the Yerawada central prison in Pune.
"Today's executions means India has taken a significant step backwards and joined that minority of countries that are still executing," said V K Shashikumar, Programmes Head at Amnesty International India in a statement.
"We recognise the gravity of the crimes for which Ajmal Kasab was convicted, and sympathise with the victims of these acts and their families, but the death penalty is the ultimate cruel and inhuman form of punishment," said Shashikumar.