A U.N. investigation into the assassination of former Lebanese Prime Minister Rafik Hariri has established links to 14 other political killings in Lebanon. A new report on the status of the probe says investigators are developing new leads as they move closer to pressing formal charges.

An interim report by Belgian prosecutor Serge Brammertz confirms that a suicide bomber detonated the massive truck bomb that killed Rafik Hariri. The 22-page report says crime scene evidence indicates the bomber was a man in his early twenties who probably was not from Lebanon.

Mr. Hariri and 22 others died in a massive blast in a Beirut suburb on February 14, 2005.

Earlier reports by Brammertz's predecessor Detlev Mehlis had implicated Syrian intelligence officials in the attack. Mehlis criticized authorities in Damascus for failing to cooperate with investigators. Syria has staunchly denied involvement, and condemned the assassination.

The latest Brammertz report avoids naming suspects, and says Syria's cooperation in recent months has been generally satisfactory.

Brammertz does, however, confirm earlier indications that the assassination was a carefully orchestrated operation carried out by a team of professionals. He says his investigators have uncovered evidence of what he calls "a complex network of telecommunications traffic between a large number" of suspects.

Brammertz also suggests the possibility of high-level involvement, saying his probe is closing in on what he calls "those who participated at different levels".

The Security Council, which authorized the probe, earlier gave Brammertz permission to expand its scope to include other political killings in Lebanon at about the same time. America's U.N. Ambassador John Bolton says the latest report establishes clear links that may shed light on who is behind all the assassinations.

"The evidence coming out in the investigation about the linkages among these 15 assassinations is significant," said John Bolton. "This is something that Mr. Brammertz himself has deemed to be important because evidence that one can uncover about all 15 investigations can have a cumulative effect in showing the pattern, the activity and perhaps the direction and control of who actually ordered the assassinations as well as how they were carried out, and who carried them out."

Bolton says the investigation appears to be moving into the final phase, when the prosecutor will present his evidence in a Lebanese court.

"The report makes plain that the investigation is getting closer to being ready for trial in a number of respects," he said. "When the report speaks of raising evidence to an evidential level, that's a sign of progress."

Last June, the Security Council gave Brammertz a year to complete the investigation. He is scheduled to brief the Council on his progress during a private meeting later this week.