The Syrian state news agency has said Saturday's bomb attack in the outskirts of Damascus was carried out by an Islamist suicide bomber.
The agency also says the attacker entered Syria from an unnamed neighbouring Arab country.
Officials say tests were being carried out on the attacker's remains to determine his identity.
Seventeen people died in the explosion, which took place near a security complex and a Shia shrine.
Such attacks are rare in Syria, but the country has seen two major assassinations in the past year.
No group has claimed responsibility for the blast, although the Syrian interior minister, Gen Bassam Abdul-Majid, called it a cowardly "terrorist act".
The official Sana news agency said a booby-trapped car packed with about 200kg (440 lbs) of explosives had blown up at 0845 (0545 GMT) on Saturday on the road to the international airport to the south of the capital, in an area crowded with civilians.
People in Damascus have been shocked by the rare attack
Security forces cordoned off the scene of the blast, which was some 8km (5 miles) from the al-Sayyida Zeinab shrine, one of Syria's holiest sites and a popular place of pilgrimage for Iraqi, Iranian and Lebanese Muslims.
All the dead are reported to be civilians. At least 14 others were wounded.
The security complex, which reportedly houses a directorate of the intelligence services that deals with Palestinian militants and political activists, suffered little damage.
The blast was the deadliest single attack in Damascus since 13 March 1986, when a bombing blamed on Iraqi agents left 60 people dead.
A month later, 144 were killed by series of bombings in five towns across Syria. The perpetrators were believed to be pro-Iraqi militants.
This is believed to be the first car bombing since a senior Hezbollah military commander, Imad Mughniyeh, was assassinated in Damascus in February.
The leader of the Lebanese Shia Islamist movement, Sheikh Hassan Nasrallah, subsequently blamed Israel for the blast, although Israel denied any involvement.
In August, a senior military official close to President Bashar al-Assad was shot dead, in as-yet unexplained circumstances, at a beach resort near the port city of Tartus.
Brig Gen Mohammed Suleiman had responsibility for sensitive security issues and was described as Syria's "main interlocutor" in a UN inquiry into the country's alleged nuclear activities.
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