India's top court upheld the death penalty on Thursday for a mastermind of the country's deadliest series of attacks and ruled a Bollywood star who bought weapons from the bombers must return to jail.Yakub Memon, brother of the alleged main plotter and fugitive Tiger Memon, was the only one of 11 convicts to see his death sentence upheld by the Supreme Court for his role in the 1993 blasts which killed 257 people in Mumbai.The judges also handed down a five-year term for the actor Sanjay Dutt for possessing illegal weapons bought from gangsters accused of orchestrating the bombings. Dutt has already served 18 months but is currently out on bail.Announcing the sentences, Supreme Court judge P. Sathashivam said the Memon brothers and another suspect, Dawood Ibrahim, who is said to be living in Pakistan, "were archers and rest of the appellants were arrows in their hands"."They were the architects of the blasts," Sathashivam, one of two judges presiding over the case, said.The remaining convicts who had appealed against the death penalty saw their sentences commuted to life imprisonment.The attacks on March 12, 1993, were believed to have been staged by Mumbai's Muslim-dominated underworld in retaliation for anti-Muslim violence that left more than 1,000 dead in the city a few months earlier.Yakub, an accountant by profession, his brothers Essa and Yusuf and sister-in-law Rubina were all convicted for their involvement in the serial blasts at 13 different locations.The Bombay Stock Exchange, the offices of the national carrier Air India and the luxury Sea Rock hotel were among the targets.Tiger Memon and Dawood Ibrahim, the other alleged masterminds of the attacks, have been on the run since 1993. Indian investigators say they were helped by Pakistan's intelligence service, a charge denied by Islamabad.Executions are only carried out for "the rarest of rare" cases in India but President Pranab Mukherjee has rejected a number of mercy pleas in the last few months, ending an unofficial eight-year moratorium.A Kashmiri separatist convicted of involvement in a deadly 2001 attack on the Indian parliament was executed in New Delhi last month while the lone surviving gunman from the deadly 2008 Mumbai attacks was hanged last November.Dutt, who was appealing against an original six-year term, spent 18 months behind bars before being bailed in 2007.During a police raid, investigators uncovered a pistol and an AK-56 rifle which were part of the consignment of weapons and explosives said to have been brought to India from Pakistan and then used in the attacks.Dutt, a one-time heavy drug user who has a reputation as one of Bollywood's bad boys, had admitted buying the weapons but insisted they were only meant to protect his family.The 53-year-old was not in court while his sister Priya Dutt, who is a member of parliament, looked visibly upset when the verdict was pronounced.His lawyer Satish Maneshinde said he has spoken to the actor who has four weeks to hand himself in to the authorities."He has accepted the judgement," said Maneshinde. "He will go through the verdict and will consider all the legal recourses available to him".The actor shot to fame in the mid-1980s in a string of action movies in which he performed his own stunts, earning him the nickname "Deadly Dutt".He is best known for playing a mobster with a heart of gold in the popular "Munnabhai" series.Dutt's first wife died of cancer while his second marriage, to a model, ended in divorce. He married for a third time in 2008.