Footage shared by the news agency showed a charred husk of the small military bus after it had been doused with water. At least three people were wounded in the blast.
It was not immediately clear whether all the dead and wounded were military personnel.
It was the deadliest known incident in the capital since 2017, when at least 30 were killed in an Islamic State attack on the Justice Palace. The capital has enjoyed relative calm for years before and since, as war raged on in the rest of the country as President Bashar al-Assad has tried to wrest control back from different groups, including a U.S.-backed Kurdish group, various rebel formations and armed Islamist organizations.
There was no immediate claim of responsibility, although most such attacks have been carried out by the Islamic State in the past.