A suicide bomber killed several people and wounded dozens in central Damascus on Friday, Syrian state television said, showing footage of what appeared to be a damaged police bus.
The television showed body parts, bloodstains and broken glass from the blast in the Maidan district, along with people shouting that this was the work of terrorists.
Several riot police shields could be seen in the wrecked bus, which was among several vehicles with smashed windows.
Immediate information indicates that a suicide terrorist blew himself up at a traffic light in the Maidan neighbourhood, the television said. There are dozens of dead and wounded, mostly civilians.
On December 23 at least 44 people were killed by what the Syrian authorities said were two suicide bombings against security buildings in the Syrian capital.
Those attacks occurred the day before the arrival in Damascus of the head of an Arab League mission that is checking Syria's compliance with an Arab plan to halt President Bashar al-Assad's violent crackdown on nearly 10 months of unrest.
The latest blast precedes an Arab League meeting in Cairo scheduled for Sunday at which a special committee on Syria is due to debate the initial findings of the observer mission.
Syria has been racked by a popular uprising against Assad in which the United Nations says more than 5,000 people have been killed. The government says armed terrorists have killed 2,000 members of the security forces since the revolt began.
The Syrian government bars most international journalists from operating in the country, making it difficult to verify accounts of incidents.
An opposition activist in Damascus said the pro-democracy movement had nothing to do with the Maidan attack, suggesting that Islamist militants might have been involved.
It seems clear that there is a growing extremist Islamist presence in Syria these days and I think there are hundreds of these extremists willing to fight the regime and blow themselves up in the name of jihad, said the activist, who asked not to be named.
We will be seeing more and more of these explosions in Syria in the coming days, I am sorry to say, he added.
(Additional reporting by Erika Solomon in Beirut; Editing by Alistair Lyon)