Amin said that the latest bombing would be of further concern to the Lebanese.
"People have their hopes pinned on the security establishment to keep the political deadlock contained ... now that the security establishment is being targeted, people feel very vulnerable and fragile," she said.
"The Lebanese have lost hope that these attacks will bring the feuding politicans together.
Several people were also injured in the blast which set ablaze several cars.
Firemen sprayed water over the blazing cars and debris scattered over the major intersection near the Mount Lebanon hospital.
Lebanon has suffered at least 30 bombings in the last three years, many hitting anti-Syrian politicians and journalists.
Elias Hanna, a military analyst and former general in the Lebanese army, said the dynamics of the attacks were changing.
"Now we are maybe seeing different targets [and] different objectives ... two weeks ago an American car was targeted by another explosion.
"Lebanon is now open – it is a theatre where everybody can settle accounts with others.
"This is a very dangerous transitional period for Lebanon since we don't have a new president," he said.
The explosion comes amid continuing discord between the majority political bloc and the opposition.
The ruling March 14 coalition has failed to reach an agreement with the Hezbollah-led opposition, which is supported by Syria, on a consensus president to replace Emile Lahoud, who stepped down in November.
"This bombing is proof that the [Syrian] mukhabarat [intelligence] have infiltrated Lebanese security services," a senior official from the March 14 coalition said, on condition of anonymity.
Syria condemned the bombing and blamed "Lebanon's enemies" for the explosion.
The explosion came 10 days after a car bomb damaged a US diplomatic car in the Lebanese capital, killing three people and wounding 16.