NEW DELHI: Supreme Court Justice Dipak Misra who had rejected Mumbai blasts convict Yakub Memon's mercy plea has received an anonymous threatening letter.

Security outside the house of Supreme Court judge Dipak Mishra has been beefed up after the threat letter was sent to his office at the Supreme Court recently.

Teams from the special cell and the intelligence Bureau have been asked to investigate the matter.

A two-tier security system has been put in place by the Delhi Police outside the judge's Tughlaq road residence. Armed guards have also been put outside the residences of the other judges.

The letter was sent to the judge office on Wednesday evening.

Delhi police have also registered an FIR in this regard at the Tughlaq Road police station.

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How Yakub's fate was sealed in less than 3 month

A three-judge bench of the Supreme Court had on July 29 unanimously rejected Yakub Memon 's petition seeking stay of his execution, putting an end to last-gasp efforts to help the 1993 Mumbai serial blasts convict escape the gallows on his 54th birthday.

"Issuance of death warrants by the TADA court against Yakub on April 30 and scheduling his execution for July 30 is in order," a bench of Justices Dipak Misra, P C Pant and Amitava Roy said, just a day after Justice Kurian Joseph and the activism of a small group seemed to have opened a window of hope for Yakub, who has been found guilty of complicity in the terrorist violence which claimed 257 lives.

A two-judge bench of Justices A R Dave and Kurian Joseph had on July 28 returned a split verdict. Justice Joseph had said there was procedural impropriety in dismissal of the curative petition filed by Yakub, who had sought reconsideration of the March 21, 2013 judgment awarding death penalty only to him.

READ IN HINDI: याकूब की अपील खारिज करने वाले जज को धमकी