BEIRUT — The assassin who killed former Prime Minister Rafik Hariri traveled from Iraq through Syria to carry out the attack, according to the Beirut judge leading the inquiry into the bombing.

Rachid Mezher, senior investigator for the Lebanese military tribunal, said the organizers had been recruited from Islamist groups linked to Syria and operating against the U.S.-led coalition in Iraq.

Investigators believe that a suicide bomber drove an explosives-laden car into the 60-year-old billionaire's convoy Monday, killing him and 16 others.

Judge Mezher said he believed that a video, in which Ahmed Abu Adas said the attack was the work of "Victory and Jihad in Greater Syria," was a genuine claim of responsibility.

Judge Mezher's opinion, however, is far from universally accepted.

Shortly after the attack, Justice Minister Adnan Addoum said the claim could be an attempt to mislead investigators, the Associated Press reported from Beirut.

Abu Adas, 23, a Palestinian Lebanese believed to have fled the country, attended two Beirut mosques known to be recruiting grounds for the Ansar al-Islam group linked to the Jordanian terrorist Abu Musab Zarqawi.

Investigators suspect that the mosques have ties to Sheik Abderrazak, a Damascus cleric who has helped terrorists travel through Syria to Iraq.

The Beirut attack bore similarities to suicide bombings carried out in Iraq by Zarqawi, who leads the al Qaeda organization in Iraq.

Abu Adas, who also spent time in Saudi Arabia, is thought to have fought in Iraq...