The Delhi Police has registered a case on a complaint filed by an advocate who alleged that he was receiving threat calls over hearing in the Prime Minister Narendra Modi's security breach case, officials said on Wednesday.

It comes against the backdrop of the ongoing hearing in the Supreme Court.

A senior police officer said that the case was registered by the Special Cell unit of the Delhi Police under relevant sections of Indian Penal Code (IPC) and Unlawful Activities (Prevention) Act.

The complainant, Vishnu Shankar Jain, told PTI that several lawyers received such threat calls last week.

"Pro-Khalistan organisation Sikhs for Justice (SFJ) called me and said that they are taking responsibility for the breach. They also asked me to convey to the judges to not hear the case," he claimed.

Several Supreme Court lawyers on Monday wrote to the apex court alleging that they have received calls threatening judges over the case involving the security breach that left Modi stuck for 20 minutes on a flyover in Punjab last week.

The letter, written by Supreme Court Advocate-On-Record Association (SCAORA), claimed that the calls were made allegedly by Sikhs for Justice (SFJ).

Earlier in the day, the Supreme Court appointed a five-member committee headed by former apex court judge Justice Indu Malhotra to probe the security breach.

The "questions cannot be left to one-sided enquiry" and a judicially trained mind needs to oversee the probe, a bench headed by Chief Justice N V Ramana said while appointing the Justice Malhotra panel.

In a "major security lapse", the prime minister's convoy was stranded on a flyover due to a blockade by protesters in Ferozepur on January 5. He returned from poll-bound Punjab without attending any event, including a rally.