India is taking the allegations regarding the assassination plot of Sikh separatist leader Gurpatwant Singh Pannun in the US seriously, the White House has said but refrained from commenting on the FBI probe into the matter and the criminal case filed by the Department of Justice.

The remarks by White House Press Secretary Karine Jean-Pierre on Monday came amid an investigative media report claiming that a RAW official identified as Vikram Yadav was involved in the assassination plot of Pannun in the US and the move was approved by the then Indian spy agency chief Samant Goel.

Pannun is one of the main leaders of the Khalistan movement and the legal advisor and spokesperson for Sikhs for Justice, which aims to promote the idea of a separate Sikh state. The Indian government has declared Pannun a terrorist.

Replying to questions on the report by The Washington Post, Jean-Pierre said an investigation is underway and the Department of Justice (DOJ) is running a criminal investigation.

"So anything specific to that I would have to refer you to the DOJ," she said.

The White House press secretary asserted that India is an important strategic partner of the United States and "we are pursuing an ambitious agenda to expand our cooperation in several areas".

About the investigative report on alleged the assassination plot, Jean-Pierre said, "We've been really consistent about that and have laid that out multiple times, whether it's a meeting here with the prime minister or a meeting abroad."

"This is a serious matter and we're taking that very very seriously. The Government of India has been very clear with us that they are taking this seriously and will investigate," Jean-Pierre said.

"We expect accountability from the government based on that. But we are going to continue to raise our concerns. That's not going to stop. We're going to continue to raise our concerns directly, with the Indian government," the press secretary added.

The alleged plot to kill Pannun in the US coincided with the June 18 fatal shooting of Khalistani terrorist Hardeep Singh Nijjar in Surrey in Canada's British Columbia province in June last year. That operation was also linked to Yadav, according to Western officials.

Both plots took place amid a wave of violence in Pakistan, where at least 11 Sikh or Kashmiri separatists living in exile and labelled terrorists by the Narendra Modi government have been killed over the past two years, the report said.

Senior Indian government officials named in the Washington Post report did not respond to it seeking comment, the daily said.

However, when asked about the investigation into the allegations made by the US in the Pannun case, Ministry of External Affairs spokesperson Randhir Jaiswal said last week, "We have set up a high-level committee. The committee is looking into information that was shared by the American side with us, because they also equally impact our national security."

The high-level committee is looking into those aspects and that is where it is right now, Jaiswal said in New Delhi on April 25.

External Affairs Minister S Jaishankar on April 1 had said that India's national security interests are involved in its investigation into the alleged involvement of a government official in the assassination plot aimed at Khalistani extremist Pannun.

The Washington Post reported that the Biden administration has refrained from making charges against Yadav.