Four bombings, including a powerful car bomb blast that rattled the Mazraa district of central Damascus, near the Russian Embassy and offices of Assad's ruling Baath Party, killed a total of 90 people and wounded at least two hundred others.
Earlier, Syrian state media put the death toll from the Mazraa bombing at 53, with more than 200 wounded. Most of those killed were civilians, including children.
Images of charred bodies lying next to mangled vehicles have been broadcasted by Syrian Al-Ekhbariya television channel.
There have been several civilians among the casualties of the bombing that was blamed on foreign-backed terrorists. Reports say more than 237 people have been wounded in the blast.
Nearby buildings were shattered by the blast, which sent thick black smoke billowing across the capital's skyline and that all roads in the area were quickly sealed off by security forces.
The Syrian news agency SANA also reported that authorities seized a car loaded with explosives in the site of the bombing in al-Thawra Street of the same neighborhood.
Shortly after the Thursday blast, two mortars were fired at a military headquarters in Damascus, Al-Ekhbariya reported.
Ambulances sirens rang out, and machinegun fire was also heard in the area.
"It is terrorism... Is that what you call Islam?" one of the wounded told Syrian television.
"Is that the freedom you want? Is that the (militant) Free Syrian Army?" said another man, speaking at the site of the attack.
The windows of the Russian embassy were also blown out by the blast, but none of its staff were hurt, Russian news agencies reported.
There have been numerous deadly attacks on civilian and government targets in the Syrian capital in recent months, among them intelligence and security buildings.
The crisis in Syria began nearly two years ago, when foreign-backed terrorists hijacked the peaceful protest of Syrian nation. Many people, including large numbers of Syrian security forces, have been killed in the turmoil.
A recent UN report revealed that terrorists from nearly 30 countries have infiltrated into Syria to fight against the Syrian government.
Meanwhile, Russia slammed the United States on Friday for employing double standards over the violence in Syria, saying Washington had blocked a U.N. Security Council’s statement condemning the Mazraa car bomb.
“We ... see in it a very dangerous tendency by our American colleagues to depart from the fundamental principle of unconditional condemnation of any terrorist act, a principle which secures the unity of the international community in the fight against terrorism," Foreign Minister Sergei Lavrov said.
There has been no claim of responsibility for the attacks, but the al Qaeda-linked hardline rebel group Jabhat al-Nusra has said it has carried out dozens of attacks in the past year, including devastating bombings in Damascus and Aleppo.