Mumbai - India on Thursday executed Yakub Memon for his role in the nation's deadliest attacks, a series of bombings in Mumbai more than two decades ago, police said.Memon was hanged at Nagpur jail in the western state of Maharashtra on the day of his 53rd birthday after last-ditch pleas for clemency were rejected by India's president and supreme court."It is complete. Yakub Memon was hanged today at 07:00," Nagpur police sub-inspector RV Halami told AFP.The Bombay Stock Exchange, the offices of Air India and a luxury hotel were among about a dozen targets of the March 1993 blasts, which killed 257 people in the deadliest attacks ever to hit India.They were believed to have been staged by Mumbai's Muslim-dominated underworld in retaliation for anti-Muslim violence that had killed more than 1 000 people.'Cruel and inhuman'Security was tightened near the targets in Mumbai on Thursday.Memon, a former accountant by profession, was the only one of 11 people convicted over the atrocity to have his death sentence upheld on appeal. The sentences on the others were commuted to life imprisonment.He denied any involvement in the blasts, during a staggered trial and appeal process that bitterly divided opinion in India and led to calls from rights activists and an ex-judge for his life to be spared.Amnesty India described the execution as "cruel and inhuman"."This execution will not deliver justice for the 1993 Mumbai blasts. It is a misguided attempt to prevent terrorism, and a disappointing use of the criminal justice system as a tool for retribution," Executive Director Aakar Patel said in a statement.Former Supreme Court judge Harjit Singh Bedi had also said reports that Memon co-operated with investigators and returned voluntarily from Pakistan, where he fled, should have been taken into account when hearing his appeal.Mercy pleasOthers pointed out that one of his brothers, Tiger Memon, was alleged to have masterminded the attacks, along with Mumbai gang boss Dawood Ibrahim. Both have been on the run since 1993.The Memon family left for Dubai in the days before the 1993 bombings, but all except Tiger were arrested when they returned to India the following year.Eight members were charged over the attacks, all of whom denied any role in the atrocity.Memon's father died during the long-running legal proceedings, three were acquitted and three others are serving life in prison, including Yakub's sister-in-law, Rubina Memon.The attack also embroiled Bollywood star Sanjay Dutt, who is serving a prison sentence for buying weapons from gangsters accused of orchestrating the bombings.Executions are only rarely carried out in India, but President Pranab Mukherjee has rejected a number of mercy pleas in the past three years, ending a de facto eight-year moratorium.The lone surviving gunman from the 2008 Mumbai attacks was hanged in 2012, while a Kashmiri separatist was executed in New Delhi the following year after being convicted of involvement in a deadly 2001 attack on the Indian parliament.The Press Trust of India reported that Memon's body was due to be handed over to his family, and Maharashtra Chief Minister Devendra Fadnavis was expected to make a statement on the execution to the state assembly later on Thursday.