A car bomb killed at least 53 people and wounded more than 200 in central Damascus on Thursday in one of the bloodiest attacks in the Syrian capital since the start of the revolt against Bashar Assad's regime in March 2011.

The apparent target was an office of the ruling Baath Party, but the blast also affected a bus station and a school and students were among the casualties, according to what authorities told Efe.

The zone of destruction was enormous, with numerous buildings damaged and dozens of vehicles burned and destroyed.

The official news agency, Sana, attributed the attack to "terrorist" groups and said that authorities discovered nearby another automobile loaded with explosives and arrested its driver.

The country's main opposition group, the Syrian National Coalition, also called the blast a "terrorist attack" and blamed the regime for the nationwide violence.

"Any act that has as its objective murdering civilians or violating human rights is an offensive and criminal act, whoever may be responsible," said the coalition in a communique.

Also, several mortar shells hit the headquarters of the Defense General Staff and army high command in the capital's central Umayyad Square, but nobody was killed in that attack.

Responsibility for the mortar strike was claimed by the Liwa al Islam extremist group.

Tens of thousands have died in Syria's internal conflict. EFE