Syria's Foreign Ministry accused armed groups affiliated with al-Qaida network of being behind the massive explosion that killed more than 53 people earlier on Thursday, the state-media said.

The ministry's statement came in a letter addressing the UN, during which it charged that al-Qaida-linked groups in Syria were receiving support from regional and foreign countries, calling on the UN to shoulder its responsibilities toward combating terrorism.

Earlier in the day, a suicide car bomber detonated his explosive-laden car at a busy intersection in the heart of Damascus near a headquarters of the ruling al-Baath party, killing more than 53 people, according to the state-media.

The oppositional Britain-based Syrian Observatory for Human Rights placed the death toll at 56, among them 15 were government soldiers. It added that another eight people, including three civilians and five regular troops, were killed in another blast that rocked Barza district Thursday.

The blasts have drawn condemnation from opposition parties.

Meanwhile, Syria's parliament condemned the blast and stressed resolution to root out terrorism. It also underlined the need to move on with dialogue to build the future of Syria. The ruling al-Baath party said in a statement Thursday that " these heinous terrorist practices indicate the bankruptcy of their perpetrators and their defeat at the hands of the Syrian army."

The statement held accountable the Arab, regional and international parties, which it said "support terrorism in Syria, supply the mercenary terrorists with arms and provide political and logistic support for them."

For his side, Minister of Religious Endowment Mohammad Abdul- Sattar al-Sayyed said that "the terrorist bombing embodies the message of terrorism and killing, which no dialogue, logic, religion or morals can accept," according to SANA.

No party has claimed responsibility for the attack but previous similar ones had been claimed by the Nusra Front, an offshoot of al-Qaida. The group has been branded as a terrorist organization by the United States.

The blast is the second huge one to rock Damascus since last May, when a suicide car bomber went off before an intelligence headquarters in al-Qazzaz area and killed 55 people.

Blasts and mortar attacks have become increasingly common in Syria as the rebels, backed by al-Qaida fighters, scaled up their attacks to wobble the government's power.