India's Supreme Court threw out on Tuesday a last-minute appeal by Yakub Memon, the only person to be condemned to death for a series of bombings in Mumbai in 1993, clearing the way for his execution after two decades in jail.
He is due to be hanged on July 30.
The blasts in March 1993 ripped through Mumbai, then known as Bombay, killing at least 257 people at separate landmarks, including the Bombay Stock Exchange, a popular cinema and two crowded markets.
Police consider Memon's brother "Tiger" Memon and mafia don Dawood Ibrahim to be the main masterminds behind the attack, carried out to avenge the destruction of an ancient mosque by Hindu zealots in 1992. Both remain in hiding, reportedly in Pakistan.
Others originally charged in relation to the attack had their sentences reduced to life imprisonment in 2013. But Memon was found by the court to be the "driving spirit" behind the attacks, and his 2007 death sentence was upheld.
While Tiger Memon has been in hiding since 1993, Yakub Memon decided to return to India from Pakistan in 1994, protesting his innocence. He was detained shortly afterwards in circumstances that remain unclear: he has said he turned himself in, but police claimed an arrest.
Amnesty International, which campaigns against the use of the death penalty, said the rejection of Memon's appeal was a "disappointing and regressive step."
"Serious questions have also been raised regarding Yakub Memon's execution and whether it is guided by political motivations," said Divya Iyer, Research Manager at Amnesty International India.
"Lawmakers in India often find it convenient to hold up capital punishment as a symbol of their resolve to tackle crime, and choose to ignore more difficult and effective solutions like improving investigations, prosecutions and care for victims' families."