According to reports in the "New York Times," the parents of Sean Smith and Tyrone Woods link Clinton's use of a private email server while secretary of state to their children's deaths.

"As a direct result of Defendant Clinton's reckless handling of this classified, sensitive information, Islamic terrorists were able to obtain the whereabouts of Ambassador Christopher Stevens and thus the U.S. State Department and covert and other government operations in Benghazi, Libya and subsequently orchestrate, plan, and execute the now infamous September 11, 2012 attack," the lawsuit says.

The claimants are also suing Clinton for allegedly making "false and defamatory statements negligently, recklessly and purposefully and/or intentionally with malice," in the wake of the attack in Benghazi.

Four US citizens were killed in the attack, including US Ambassador Christopher Stevens.

Mother of Sean Smith and supporter of Clinton's Republican opponent Donald Trump, Patricia Smith, said at the Republican national convention last month that she blamed Clinton "personally" for the death of her son.

'No evidence of wrongdoing'

Despite several investigations by congressional Republicans into the Benghazi attack, the Democrat presidential candidate has never been found directly at fault. The existence of her private email server was revealed in the process, however, triggering a separate year-long FBI investigation.

In response to Monday's lawsuit, Clinton campaign spokesman Nick Merrill stressed that the Benghazi attacks have been exhaustively investigated.

"While no one can imagine the pain of the families of the brave Americans we lost at Benghazi, there have been nine different investigations into this attack and none found any evidence whatsoever of any wrongdoing on the part of Hillary Clinton," Merrill said.

FBI Director James Comey also said last month that there weren't grounds to prosecute Clinton. He added, however, that Clinton and her aides had been "extremely careless" in their handling of classified information.

Mark Zaid, a Washington lawyer who specializes in national security issues, predicted the lawsuit would be thrown out of court quickly.

"It has no chance of success whatsoever. It's fundamentally and fatally flawed based on its legal and factual assertions," said Zaid.

The lawyer has filed several lawsuits seeking State Department records from Clinton's tenure and also has provided advice to the Republican National Committee on obtaining Clinton records.

ksb/bw (AP, dpa)