NEW DELHI : India's top court on Monday stayed the execution of a key plotter of the country's deadliest series of attacks.Yakub Memon, brother of the alleged main plotter and fugitive Tiger Memon, had been sentenced to death for his role in the 1993 blasts which killed 257 people in Mumbai.The attacks on March 12 that year 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.A panel of two Supreme Court judges referred Memon's petition against his sentence to a higher bench of the same court which will decide whether the review should be held in open court, the Press Trust of India news agency reported.In the meantime the "execution proceedings will remain stayed", one of the judges told the court.Yakub Memon, an accountant by profession, his brothers Essa and Yusuf and sister-in-law Rubina were all convicted of involvement in the blasts at 13 different locations. He has been in jail for two decades.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.The bombings also embroiled Bollywood star Sanjay Dutt who was convicted and spent time in jail for buying weapons from gangsters accused of orchestrating the bombings.Memon is challenging a recent rejection of his mercy petition by President Pranab Mukherjee, saying others convicted over the blasts have had their death sentences commuted.The Supreme Court last year rejected Memon's appeal for clemency. A judge at the time declared him, his brother Tiger and Dawood Ibrahim to be "architects of the blasts". Memon was the only one of 11 people convicted for the 1993 attacks to have his death sentence upheld. The sentences on the others were commuted to life imprisonment.The court's decision on Monday follows a landmark ruling in January that places new restrictions on executing prisoners in the world's biggest democracy.The supreme court in January commuted the death sentences of 15 convicts, ruling that "inordinate and inexplicable" delays in carrying out executions were grounds for reducing their original punishments.With more than 400 people on death row in India, that ruling is expected to have consequences for a huge backlog of cases.A Sikh militant, convicted of a deadly car bombing two decades ago, was spared execution in March after the court commuted his death sentence.India has carried out three executions in the last decade following an eight-year unofficial moratorium from 2004 to 2012.