The reports blame "terrorists" and say 30 people were wounded by the blast on April 27 in the city's al-Midan district.
Earlier on the same day, activists reported a separate explosion near a state-owned company in an industrial zone of Damascus.
A wave of explosions has rocked Syrian cities in recent months, despite a diplomatic push to end an uprising against President Bashar al-Assad that began over a year ago.
UN Secretary General Ban Ki-moon says Assad's regime is "in contravention" of an internationally agreed ceasefire plan.
The White House said on April 27 that it is disappointed at Assad's failure to live up to commitments under the plan, and that Washington will raise international pressure on his regime.