Indian national Nikhil Gupta, accused of being involved in a murder-for-hire plot against a Sikh extremist on American soil, pleaded not guilty as he was arraigned in federal court here.

Gupta was extradited to the US from the Czech Republic on June 14, which court records show as the day of his arrest in the US.

He made his first appearance in Manhattan federal court before Magistrate Judge James Cott on Monday afternoon for his arraignment and pleaded not guilty. Gupta's attorney Jeffrey Chabrowe entered the "not guilty" plea on his behalf. Gupta is being held in a Brooklyn detention facility.

Gupta is charged with murder-for-hire and conspiracy to commit murder-for-hire. If convicted, he faces a maximum sentence of 10 years in prison for each charge.

The next court hearing in the case is on June 28. Court records show that a status conference has been set for June 28 before Judge Victor Marrero. During the initial appearance, Gupta's lawyer told the judge that his client is a vegetarian and had not been provided a vegetarian meal in the detention facility.

US Attorney General Merrick Garland said in a statement that Gupta's "extradition makes clear that the Justice Department will not tolerate attempts to silence or harm American citizens".

Deputy Attorney General Lisa Monaco termed the extradition a "vital step toward justice, and I am grateful to our Czech partners for their assistance in this matter".

US Attorney Damian Williams for the Southern District of New York said the extradition "makes clear our unwavering resolve to investigate, thwart, and prosecute those who seek to harm and silence US citizens here and elsewhere".

Gupta was arrested in the Czech Republic last year at the request of the US government on charges of being involved in a plot to assassinate Khalistani separatist Gurpatwant Singh Pannun in New York. Pannun holds dual American and Canadian citizenship.

A handful of Pannun's associates and supporters had gathered outside the court house and one was seen holding a Khalistani flag.

Last month, the Czech Constitutional Court rejected a petition by Gupta against his extradition to the US to face the charges.

US federal prosecutors allege that Gupta had been working according to the directions of an unnamed Indian government official.

India has, however, denied its involvement in the case and has instituted a high-level investigation into the allegations.

"This is a complex matter for both our countries," Gupta's attorney Chabrowe told PTI ahead of his client's arraignment.

"It is extremely important that we refrain from rushing to conclusions so early in the process. Background and details will develop that may cast government allegations into an entirely new light," he said.

"We will pursue his defence vigorously and ensure he receives full due process, regardless of outside pressures," he added.

Federal prosecutors allege that Gupta hired a hitman to kill Pannun and paid USD 15,000 in advance.

Gupta, through his attorney, has denied the charges and said that he has been "unfairly charged".

The Washington Post reported in April that Vikram Yadav, a Research and Analysis Wing (R&AW) officer, was the Indian official behind the plot. The paper also said the then R&AW chief Samant Goel sanctioned the operation.

India's Ministry of External Affairs, however, dismissed the report, saying it makes "unwarranted and unsubstantiated imputations" to claim that Indian agents were involved in the plot to kill Pannun.

India has publicly said a high-level inquiry is looking into the evidence shared by the US in the alleged plot to kill Pannun.