"Shells hit the Fardos mosque in al-Jubeileh neighbourhood at evening prayers, the last before Ramadan. The mosque was packed. Around 20 people were pulled from the rubble with missing limbs and bad wounds. The number of dead will likely rise," Abu al-Tayeb al-Deiri, one of the activists, told Reuters from the desert city 430 km (270 miles) northeast of Damascus.
Syrian authorities have banned most independent media from the country, making independent verification of events on the ground difficult.