Commentators said Syria would most likely be blamed for the killing and as a result feel the repercussions hardest.
But many of them wondered what Damascus stood to gain from having a hand in al-Hariri's death.
"What exactly would the Syrians gain from this? Precisely because most people would say that this is the Syrians who have done this. It doesn't make any sense," Rime Allaf, Middle East analyst at the Royal Institute for International Affairs in London, UK, said.
"The first people who will be hurt by this is Syria. Given the chaos in Lebanon and the rising anger between the factions, analytically Syria loses a lot by this," Allaf told Aljazeera.net.
The killing was condemned by Syrian and Lebanese government officials.
Although a previously unheard of outfit calling itself al-Nasir and Jihad Group in al-Sham claimed responsibility for al-Hariri's assassination, commentators said the magnitude of the blast suggested an intelligence agency was behind the explosion rather than a small group.
Public opinion is polarised over
Syria's 14,000-strong presence
Reuters reported security sources as saying the explosive device was sophisticated enough to evade jamming equipment so hi-tech that al-Hariri's passing convoy would interfere with cellphones and televisions.
So who plotted al-Hariri's violent death? Murhaf Jouejati a Syrian analyst at the Middle East Institute in Washington, told Aljazeera.net that it was too early to accuse anyone of being behind the killing.
"This is not good news. The Syrians are not crazy and they are not going to be assassinating Lebanese officials," he said.
"They (the Syrians) have been engaging in dialogue with the opposition ... I think there are many local parties who would have an interest in the destablisation of Lebanon."
Al-Hairiri had recently joined the opposition in their calls for Syria to withdraw the 14,000 Syrian troops from Lebanon. He resigned from his position as prime minister last October after President Emile Lahud had his term extended, a decision that many saw as being imposed by Syria.
A billionaire businessman who had played a key role in the post-war reconstruction process in Lebanon, al-Hariri was a leader of Lebanon's Sunni Muslim community.
Al-Hariri had recently joined calls
for withdrawal of Syrian troops
Michael Young, a Lebanese political analyst and opinion editor of Lebanese newspaper The Daily Star, said the repercussions for Lebanon and Syria would be grave.
"It may very well strengthen the opposition to the Syria presence. There will be a fierce reaction from the Sunni community. I think the government is very embarrassed. They may have to pay for the backlash," he told Aljazeera.net.
Young said Damascus may be blamed for the killing and that this would have an effect on Syria's already tense relations with the US.
"It becomes a question of how much the US and France want to escalate against Syria. The Americans will hold Syria directly responsible. They will not seek conciliation over Resolution 1559. UN envoy Terje Roed-Larsen was seeking a delay in its implementation, but now I think there will be no delay," he said.
Plea for calm
Despite some suggestions that al-Hariri's killing could mean a return to the dark days of Lebanon's civil war that killed more than 100,000 people and raged between 1975 and 1990, Young was keen to make the point that he did not think there would be a resurgence in inter-communal violence.
"This is a political assassination. This is not the beginning of the civil war. We are not seeing Lebanese fighting each other," he said.
Lebanese opposition MP Boutros Harb echoed Young's view and said it was important now to ensure that calm prevailed in Lebanon.
Opposition MP Marwan Hamada
survived a car bombing last year
"Its our duty to avoid a choatic situation," he told Aljazeera.net.
"There are some parties who may have big interest in the disappearance of al-Hariri and disturbing the peace. They are expecting to create chaos. This is a very dangerous," he said.
However other analysts were more candid and pointed to the assassination attempt on Marwan Hamada. Hamada, a Druze MP, is a former minister who resigned in protest over the decision to extend Lahud's term and survived a car bomb attack in October.
"Whatever happens, the reaction will be against the Syrians. It's obvious. What happened with Marwan Hamada was also very obvious. Being obvious is the name of the game these days," a Lebanese observer told Aljazeera.net on the condition of anonymity.