Kassir's car blew up as he switched on its ignition outside his house in the Christian neighbourhood of Ashrafiyeh in Beirut on Thursday.
Hours after removing Kassir's body from the wrecked car, the stench of blood was still in the air.
Lebanese soldiers sealed off the area. But they could not turn back journalists from getting close enough to their colleague's car.
"Get back, please get back," a soldier told a crowd of journalists and onlookers just a few meters away from the mangled grey Alfa Romeo car.
An angry young journalist shouted at the soldiers, accusing them of doing nothing to protect Kassir. "He's my teacher and he's lying in front of me torn apart while all you care about is that I shouldn't get one metre closer to the car."
"If you wanted to do something useful, you should have protected him before he got killed," said Kassir's young colleague before disappearing into the crowd.
Kassir, a columnist at the leading Lebanese daily An-Nahar was well-known for his anti-Syrian writings and his criticism of what he called the "Lebanese police state".
He was a leading activist of the Democratic Left, which was among the opposition groups organising anti-Syrian protests that were staged shortly after the assassination of former Prime Minister Rafiq al-Hariri on 14 February.
Kassir was a leading activist of
the Democratic Left
His killing sparked anger among people visiting the site of the blast with many of the view that Damascus continued to wield influence in Lebanon despite a Syrian troop withdrawal that was completed on 26 April.
Anti-Syrian sentiments have been running high in the country since al-Hariri's assassination.
It was widely believed that Syria was behind his killing although no evidence has been produced yet to support this claim.
But a United Nations mission to investigate the former premier's killing charged Syria of bearing "primary responsibility for the political tension that preceded" the assassination.
"Lebanon is not 100% clean yet," General Issam Abu Jamra, who returned to Lebanon with Christian opposition leader Michel Aoun on 7 May after 14 years of exile, told Aljazeera.net as he inspected the site of the explosion.
"Changes should be made from top to bottom," he said. "You cannot erase 30 years of Syrian control (of the country) in just a few days. It's impossible," said Dori Chamoun, the head of the Christian National Liberal Party.
Chamoun told Aljazeera.net that the formation of a new government and the sacking of some pro-Syrian security chiefs did not mean that "Lebanon has become completely safe and insured from many abuses like the ones we had today."
Kassir's murder was described as
a political assassination
Chamoun described Kassir's murder as a political assassination. "Samir Kassir was a writer who had his many strong opinions against Syrian occupation and about the whole apparatus of the Syrian operation (in Lebanon) and I'm sure this must have something to do with it."
Lebanon's Prime Minister Najib Mikati, who formed the new government in April, removed a number of powerful pro-Syrian security chiefs and replaced them with figures acceptable to the opposition and the al-Hariri family.
However, other security chiefs, such as Colonel Mustafa Hamdan, the commander of the Republican Guards Brigade and a close protégé of Lebanese President Emile Lahoud, have retained their posts.
But President Lahoud's spokeman Rafik Shalal described Kassir's killing as "a grave incident," saying that the president had ordered an investigation.
"It is better not to throw accusations until the circumstances are uncovered," he told an Arab satellite channel.
Reporters Without Borders Secretary-General Robert Ménard, who is currently in Lebanon, described Kassir's assassination a "cowardly murder."
"We have lost a friend, and press freedom has lost a passionate defender," he said in a statement.
Ménard added : "The French authorities and the UN commission investigating the assassination of Rafiq al-Hariri should pay particular attention to this new act of terrorism."
"Those responsible for the murder, which targeted a great journalist, must be identified, arrested and punished. We promise to remain mobilised until justice has been done"
"Those responsible for the murder, which targeted a great journalist, must be identified, arrested and punished. We promise to remain mobilised until justice has been done."
Lawmaker Ghassan Mokhaiber described Qassir as among the "freest voices of the printed press" in Lebanon.
"The target is indeed freedom of the press in Lebanon and free voices. He was a free thinker and a staunch critic not only of Syrian interference in Lebanon but also of the Syrian government from within," said Mokhaiber, who is also a human rights activist.
Although Mokhaiber ruled out a possible linkage between Kassir's assassination and the legislative polls being held in Lebanon, he said that the murder would set a "horrible mood for the elections."
Samir Kassir is married to Giselle Khouri, the presenter of Bi al-Arabi, a political programme aired on the al-Arabiya channel.