"Initial information of a terrorist explosion in the Midan neighbourhood of Damascus," state television reported in a breaking news alert, giving no further details.
The Syrian Observatory for Human Rights, a Britain-based monitor, reported "at least two blasts" hit the neighbourhood.
It said the first was a car bomb attack near a police station and the second was caused by a suicide bomber.
The monitor said there were also reports that a second suicide bomber had detonated an explosive belt in the attack.
There was no official confirmation of those details, although the Al-Watan newspaper, which is close to the government, also reported the attack was near a police station in Midan.
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But the capital has been rocked by sporadic bomb attacks.
In December 2016, three police officers were wounded when a seven-year-old girl walked into a police station in Midan wearing an explosive belt that was remotely detonated.
More than 330,000 people have been killed in Syria since the conflict began.