The killing in Beirut, in which Hariri and at least nine other people died when an explosion ripped through his motorcade, has been condemned by leaders in the Middle East, Europe, North America, and elsewhere.
A previously unknown militant group has claimed responsibility for the attack, saying it killed Hariri in a suicide operation because of his ties to Saudi Arabia. That claim could not be independently confirmed.
Lebanese Justice Minister Adnan Adoum urged caution in assessing such statements.
"There will be many of claims [or responsibility] from various groups to mislead the investigation," Adoum said. "Nothing is clear right now."
Lebanese opposition leaders have accused the governments of Lebanon and Syria, which maintains some 15,000 troops in Lebanon but has come under international pressure recently to withdraw them, of bearing responsiblity for the death of Hariri, a wealthy businessman who resigned as prime minister in October.
The Syrian government denied playing any role and has condemned the assassination.
UN Secretary-General Kofi Annan expressed concern about Lebanon's stability, saying he hoped the killing would not reignite the country's 1975-90 civil war.
The White House called Hariri a strong supporter of Lebanese independence and said President George W. Bush was "shocked and angered" by the assassination.
Spokesman Scott McClellan said the United States would consult other members of the UN Security Council about punishing the perpetrators of the assassination.
The Security Council, which last year passed a resolution demanding that Syrian troops leave Lebanon, is due to meet later today to discuss the situation.
(Reuters/AP/AFP)Related stories:"Massive Beirut Blast Kills Former Lebanese Premier""Middle East: Analysts Say Hariri's Death Signals Difficult Period Before Lebanese Elections"
and"Middle East: World Reacts To Assassination Of Former Lebanese Prime Minister"