Nikhil Gupta, who has been accused of involvement in an alleged plot to assassinate a Sikh separatist, has been extradited to the United States. Gupta was arrested in the Czech Republic on June 30 last year and the US had sought his extradition.

The Federal Bureau of Prisons inmate records on Sunday showed him locked up in the Metropolitan Detention Centre in Brooklyn, where prisoners due for appearances in federal courts here are kept.

According to a spokesperson for the federal court of the Southern District of New York, quoted by NBC TV network, he is scheduled to appear in court on Monday.

His extradition was held up by his appeal to the Czech Constitutional Court earlier this year against his extradition, which was rejected last month clearing the way for him to be sent to the US.

The alleged plot raised concerns in the US because an Indian police officer is accused of masterminding it.

According to court documents, Gupta, who also uses the name “Nick”, is charged with participating in a plot with an unnamed Indian “senior field officer” to assassinate the leader of a “US-based organisation that advocates for the secession of Punjab state” and the establishment of a “Sikh sovereign state called Khalistan”.

The group’s leader, who is not named in the court documents, is Gurpatwant Singh Pannun, a lawyer with US and Canadian citizenships, who lives in New York and runs a campaign for Khalistan.

He is designated as a terrorist by the Indian government.

In a filing in the New York court in January, Gupta’s lawyer Jeffrey Chabrowe said that according to his family’s media interviews he “faces basic human rights violations while in custody in Prague” and was kept in “extended” solitary confinement without consular access.

According to the charging document in the court, Gupta was recruited by the “senior field officer” to “orchestrate the assassination.”

He, in turn, the document said, contacted a person he believed was a “criminal associate, but was, in fact, a "confidential source working with US law enforcement”.

That person introduced him to a “purported hitman” who was an undercover US law enforcement officer who was offered $100,000 to carry out the assassination, the document said.

Gupta arranged for an advance of $15,000 to be delivered by an associate to the presumed “hitman”, who was also given details about Pannun and also told him that a Canada-based Khalistan leader Hardeep Singh Nijjar, who was killed in British Columbia, had been a “target”, according to the document.

The prosecution said that he had himself described his “involvement in narcotics and weapons trafficking” and asked the “senior field officer’s” help in getting cases against him in India dismissed.

Gupta’s lawyer Charbrowe asked the court in January to compel the prosecution to provide more details about the case to the defence to enable it to defend him.

He said that according to Gupta’s Czech lawyer Petr Slepica, the defendant had been interviewed several times by “groups of senior US officials” while the lawyer has not been given any documents about the case except for indictment – the charging document.

Federal Judge Victor Marrero dismissed the request saying that under the Rules of Criminal Procedure, the prosecution has 14 days after Gupta is produced in court to give the information to the defence.

State Department Spokesperson Matthew Miller said in April that “we have made clear to the government of India that we want to see them conduct a full investigation, and we continue to look forward to the results of that investigation”.