NEW DELHI — India's Supreme Court on Thursday upheld the weapons conviction of Bollywood leading man Sanjay Dutt and ordered him to report to prison within four weeks in a case linked to the deadliest terror attack in Indian history. Dutt's failed appeal of his conviction was part of a broader ruling by the Supreme Court on cases stemming from the 1993 bombings that killed 257 people in the financial hub of Mumbai. A total of 100 people were convicted of involvement in the blasts. The court upheld the death sentence given to Yakub Memon, who is a brother of Ibrahim ‘Tiger' Memon, an accused mastermind of the bombings who remains at large. However, the court commuted to life in prison the death sentences given to 10 other men convicted of carrying out the blasts. Some of the men have been in prison for nearly two decades. Dutt originally had been sentenced to serve six years in prison on the charge of possessing an automatic rifle and a pistol that were supplied to him by men subsequently convicted in the bombings. He served 18 months in jail before he was released on bail in November 2007 pending an appeal in the top court. The court shaved one year off his sentence Thursday and ordered him imprisoned within a month to finish out the remaining 3 1/2 years of his sentence. Dutt had earlier been acquitted of the more serious charges of terrorism and conspiracy. The actor's case was part of a sprawling Mumbai bombings trial that has dragged on for 18 years. Dutt maintains he knew nothing about the bombing plot and that he asked for the guns to protect his family — his mother was Muslim and his father Hindu — after receiving threats during sectarian riots in Mumbai. Dutt's lawyer Satish Maneshinde said the 53-year-old actor would take some time before deciding on his next step. For now, Dutt will “abide by the apex court's order of undergoing the sentence of 3 1/2 years in letter and spirit,” Maneshinde said. “Three-and-a-half years is not a long period,” he said. The 1993 bombings were seen at the time as the world's worst terrorist attack, with 13 bombs exploding over a two-hour period across Mumbai. Powerful explosives were packed into cars and scooters parked near India's main Bombay Stock Exchange and other sites in the city. Apart from the 257 dead, more than 720 people were injured in the attack. The bombings were believed to have been acts of revenge for the demolition of a 16th-century mosque by Hindu nationalists in northern India in 1992. After the demolition, religious riots erupted, leaving more than 800 people dead, most of them Muslims. The court's ruling on Dutt comes as a blow for Mumbai's film industry, putting several films he was working on in limbo. Despite his brush with the law and his stint in jail, Dutt's Bollywood career flourished over the past two decades. He gained enormous popularity for a series of Hindi films in which he played the role of a reformed thug who follows the teachings of nonviolence advocate and Indian independence hero Mohandas Gandhi. Industry estimates said Dutt was currently involved in projects worth at least $20 million. — AP