|The blast is the latest in a string of attacks |
blamed on Syria and their proxies [AFP]
Zeina Khodr, Al Jazeera's correspondent in Beirut, said the March 14 bloc was preparing to issue a statement blaming Syria.
The Lebanese government announced a period of mourning in the aftermath of Ghanem's murder.
The education ministry said all schools and universities will remain closed until Friday.
Fearing for his life, Ghanem had fled into exile following the assassination in June of Walid Eido, another anti-Syrian MP from the March 14 bloc, and only returned to Lebanon on Sunday.
Ghanem's death has reduced the bloc's majority in parliament to 68 members out of the 127-member house, with numbers set to play a key role in the presidential vote.
"This is an attack aimed at sabotaging all efforts to reach a solution to the current political crisis," Butros Harb, an MP and presidential candidate, said.
"You cannot separate this killing from the presidential election."
Wael Abu Faour, a Druze MP, said on Wednesday: "Syria wants to prevent the majority from remaining a majority by assassinating its members.
"Syria wants to prevent the majority from electing a president from among its ranks."
Nayla Moawad, the Lebanese minister of social affairs, told Al Jazeera: "It is clearly an attempt to diminish the number of members of parliament from the majority and of the March 14 Forces.
"It proves that there is a mainstream, led by Iran and Syria, against Lebanese sovereignty.
"It is the end of any dialogue. We will not dialogue with murderers and we will not dialogue on the blood of our martyrs."