A senior Lebanese intelligence officer was seriously wounded and two companions were killed by a bomb that exploded in their car near the southern city of Sidon today.
The officer, identified as Colonel Samir Shehadeh, works for the Interior Ministry's intelligence branch.
Police said one of the two men killed was in uniform, the other in plainclothes. There was no claim of responsibility for the attack in the coastal village of Rmeileh.
Mr Shehadeh was among officers involved in Lebanon's investigation into last year's assassination of former Prime Minister Rafik al-Hariri.
The attack occurred ahead of a report this month by UN investigator Serge Brammertz on his inquiry in Mr Hariri's killing.
The Lebanese government plans in the next few weeks to authorise an international tribunal to try the culprits.
An initial UN report said Syrian security officials and their allies in Lebanese security agencies were involved in the bombing that killed Mr Hariri in Beirut on February 14th, 2005.
Damascus has denied any role in the assassination, which led to the withdrawal of Syrian troops from Lebanon in April 2005.
Mr Hariri's death was followed by more than a dozen bombings that killed or wounded anti-Syrian politicians and journalists. The last such attack killed prominent Christian journalist and member of parliament Gebran Tueni on December 12th.