"Six people were killed when three shells (likely launched by rebels) hit Baghdad street, in the centre of the city. Nine others were killed in a massive (regime) shelling of Qaboon in northwestern Damascus," said the Syrian Observatory for Human Rights.
Several people were also wounded, the Britain-based watchdog said without giving further details.
"Shelling and clashes have raged non-stop in Qaboon all throughout the day," said the watchdog, which relies on a broad network of activists, doctors and lawyers for its reports.
The rebels fighting to topple the regime of Syrian President Bashar al-Assad have also stepped up shelling attacks on Damascus.