PARIS — Hackers broke into a major Lebanese news Web site and plastered the front page with the names of the so-called secret witnesses for the trial in the killing of the former Prime Minister Rafik Hariri in an apparent bold, new move to intimidate witnesses and derail the trial.

The hacking of the Beirut newspaper last week came on the heels of an earlier publication by another Lebanese newspaper that named 32 witnesses in the trial, which is planned to begin this year. Progress in the case at the United Nations-backed Special Tribunal for Lebanon has been delayed for years by blocked investigations in Beirut, the killing of a Lebanese investigator, the near-killing of another and the court’s bureaucracy.

A spokesman for the tribunal denounced the hacking operation, warning that the authors were endangering the lives of Lebanese citizens. “It is part of the continuing campaign to undermine the tribunal and intimidating all of the witnesses,” the spokesman, Marten Youssef, said Friday.

International criminal tribunals have been confronted by threats to witnesses and the disclosure of confidential materials before, and a number of lawyers and journalists have been prosecuted for contempt of court. But until now, international courts have not faced a cyberattack of this scale, according to lawyers in The Hague.