Nobody was hurt in the melee at a private gynecology clinic, which underscored the charged emotions behind the international tribunal looking into the 2005 assassination. The Hague-based court said the incident was being taken seriously.

The tribunal has not yet indicted any suspects in the assassination, but speculation that the court could name members of the Hezbollah group has raised fears of violence between the heavily armed force and Prime Minister Saad Hariri's allies.

Wednesday's incident happened at a clinic on the first floor of a residential building in Beirut's southern suburb of Ouzai, a Hezbollah stronghold. It was unclear what role the clinic may play in the investigation.

Dr. Iman Sharara, who runs the clinic, said two men — an Australian and a French national — showed up with a Lebanese interpreter for an appointment to go through some phone records. She said the men requested the phone numbers of up to 17 patients who had visited her clinic since 2003.

When she went outside to speak to her secretary, she saw a large group of women force their way into the clinic, screaming and trampling on documents belonging to the clinic.

"It looked like a real battle," she told reporters. "The investigators fled. The interpreter, they pulled her hair, they snatched things from them ... I returned to my clinic, hid inside and called my husband."

A police officer said more than 30 women stormed the building, with another 75 or so remaining outside. He added, on condition of anonymity because he was not authorized to give public statements, that the crowd shouted curses at the tribunal and one protester stole an investigator's briefcase. It was not known what was inside.

Hezbollah's Al-Manar TV station called the investigators' intrusion on a private clinic "scandalous." It quoted witnesses as saying female patients at the clinic became angry when they saw two foreign investigators walk in.