Syrian state TV is reporting an explosion in a southern neighborhood of the capital, Damascus.
It says the Sunday morning blast, which happened during rush hour on the first working day of the week, appears to have been “a terrorist act”.
The UK-based Syrian Observatory for Human Rights told AFP news agency that the explosion struck near a military intelligence office in Damascus.
“The explosion took place near a security branch in the south of the city. There are some people killed and injured but we could not verify the toll immediately,” the monitor said in a statement.
It was unclear if the blast was caused by a bomb that was planted or a suicide attack, the monitor said, adding that shooting followed the explosion.
State media say all roads leading to the scene of the blast have been closed.
Attacks have been rare in Damascus since Syrian government forces captured the last rebel-held neighbourhoods and suburbs of the capital last year.
Such blasts had left hundreds dead over the course of the nearly eight-year civil war.