A legal team representing survivors and familes of victims of the 9/11 attacks has accused Saudi authorities of trying to silence several witnesses.

An almost two-decades-old lawsuit brought to court by thousands of victims and their families accuses Saudi officials of having ties to the 11 September 2001 attacks on New York and Washington. About 3,000 people were killed.

On Wednesday, lawyers representing the families said that four of their witnesses in the case had been threatened or intimidated by alleged Saudi agents.

On those grounds, the plaintiffs' legal team requested that the identities of the witnesses in the drawn-out legal battle be protected and kept secret.

Lawyers representing the Saudi government denied the allegations of witness tampering, saying the claims were "based on hearsay within hearsay".

The defense also accused the plaintiffs' lawyers of trying to gain a "tactical advantage" in legal deposition interviews with witnesses set to be organised later this month.

Jamal Khashoggi: 'A potential witness'

The lawyers of the 9/11 victims invoked the 2018 murder of journalist Jamal Khashoggi by Saudi officials in Turkey as evidence of the kingdom's potential threat against their witnesses.

The 9/11 lawsuit looming over Saudi Arabia's ambitions Read More »

Andrew Maloney, one of several attorneys representing the plaintiffs, also for the first time revealed that Khashoggi, an ardent critic of the Saudi government, had been "a potential witness" before he was murdered.

"He had valuable information," Maloney told the judge on Wednesday.

Maloney, during the emergency hearing that took place at a federal court in lower Manhattan, did not provide further details regarding what that information might have been.

US Magistrate Judge Sarah Netburn said she was "troubled by the allegations" and asked for a submission from the plaintiffs’ lawyers detailing the claims to be turned in by 18 March.

"I take these allegations incredibly seriously," Netburn said.

'Absolutely false'

In court papers, Maloney described some of the allegations made by the four witnesses who said they feared they were being targeted by Saudi officials.

One witness said his family had been approached and "directly threatened by Saudi government officials" within the past year, Maloney wrote. He said the witness was given to understand that he or his relatives "would be murdered" if he spoke out.

Another potential witness said that relatives in Saudi Arabia "feared for their lives", Maloney said. A third reported being stalked, and another was reportedly thinking of buying a bulletproof vest.

He added that law enforcement authorities had been notified of the alleged threats.

"We categorically deny these allegations," said Michael Kellogg, a DC-based lawyer representing Saudi Arabia.

Kellogg accused the plaintiff's legal team of trying to "pick and choose which witnesses will testify".

"We should be allowed to know who these witnesses are," Kellogg told Judge Netburn. "We think these allegations are absolutely false."

Following Kellogg's statements, the plaintiffs' lawyer accused the defense of wanting to know the identities of the witnesses so that Saudi officials could be notified and "dissuade them from testifying".

"[No] Saudi Arabian government official, employee, agent, or anyone acting on Saudi Arabia's behalf has attempted to threaten any potential witness or any witness's family members in this proceeding," a Saudi government minister said in court papers.

Saudi diplomat linked to 9/11

The US government has never released documentation indicating that the Saudi government was involved in 9/11.

US judge allows 9/11 lawsuits against Saudi Arabia to proceed Read More »

Still, last year during a meeting at the White House with victims' families on the anniversary of the attacks, US President Donald Trump promised the visitors that he would order the attorney general to release the name of a Saudi diplomat who had apparently been linked to 9/11 in an FBI report years earlier.

The next day those hopes were dashed, as Attorney General William Barr said the release of such records would not be possible.

Their disclosure risked "significant harm to the national security," Barr said at the time.

The Saudi government has long denied involvement in the 9/11 attacks.

In March 2018, a US judge in New York rejected Saudi Arabia's request to dismiss the lawsuit.