Lebanon's pro-Western government says it is determined to hold a presidential election, despite the assassination of another anti-Syrian politician.
Lebanon will not be cowed by the bombers, the government says
Prime Minister Fouad Siniora said the killers of MP Antoine Ghanim would not be allowed to succeed in their aims.
Syria has been accused of being behind the killing, but it denies involvement.
MPs are due to choose a new president next week. The killings of several anti-Syrian figures have left Lebanon's government with only a slim majority.
Banks, schools and government offices have been closed in Lebanon, as the country mourns Mr Ghanim, of the Maronite Phalange party.
The education ministry said schools and universities would remain closed again on Friday, when a funeral would be held.
Mr Ghanim died with at least six others in a car bombing in the mainly Christian Sin al-Fil district on Wednesday.
Mr Siniora said on Thursday: "The hand of terror will not win and will not succeed in subduing us and silencing us.
"The Lebanese will not retreat and will have a new president elected by lawmakers, no matter how big the conspiracy was."
He has called for a UN investigation into the assassination of Mr Ghanim, who had returned to Beirut just a few days before his death to take part in next week's vote.
Lebanon is poised to choose a successor to pro-Syrian President Emile Lahoud.
The country has been mired in an ongoing political crisis, with a deadlock between pro- and anti-Syrian factions in parliament.
'Hand of terror'
Syria said it had no involvement in the attack, calling it a "criminal act" that undermined hopes for Lebanese national reconciliation.
Feb 2005: Ex-PM Rafik Hariri
April 2005: MP Bassel Fleihan
June 2005: Anti-Syria journalist Samir Kassir
June 2005: Ex-Communist leader George Hawi
Dec 2005: Anti-Syria MP Gebran Tueni
Nov 2006: Industry Minister Pierre Gemayel
June 2007: Anti-Syria MP Walid Eido
Sep 2007: Anti-Syria MP Antoine Ghanim
But some Lebanese politicians were quick to blame Damascus for the blast.
Saad Hariri, son of Rafik Hariri, a former prime minister who was assassinated in a bomb attack in 2005, said responsibility lay with the "cowardly regime" of Syria.
Even pro-Syrian Mr Lahoud said it was no coincidence someone was killed whenever there were positive developments in Lebanon.
US President George W Bush denounced the "horrific assassination", which he described as attempts by Syria and Iran to destabilise Lebanon.
The attack has also been criticised by the UK, the EU, Russia, China, France and Italy.
Six other leading figures in Lebanon's anti-Syria movement have been killed since Rafik Hariri's assassination in 2005.