Syrian regime bombing raids struck rebel positions around Damascus on Wednesday in a bid to dislodge insurgents entrenched on the outskirts of the capital, a military source told AFP.
"The army began a military operation this morning with the aim of expanding a security zone around areas controlled" by the government, the source said.
"It began in Jobar with limited, precise and effective operations against lines of defence used by armed groups to observe the rest of the capital," the source said, adding that "Syrian aircraft are in action but not Russian ones".
Russia has since last month conducted bombing raids in Syria.
Jobar neighbourhood, in eastern Damascus, has been a battleground for more than two years. Nearly all of its pre-war population has fled, and fighting between the Syrian army and rebel groups has devastated the suburb.
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The area is highly strategic as it sits near the Abbasid Square roundabout that leads directly to the heart of Damascus and also provides access to Eastern Ghouta, a region east of the capital also in rebel hands.
The Syrian army has attempted on several occasions to retake Jobar.
"Artillery fire, rockets and other projectiles started at around 6 am (0300 GMT) and lasted for three hours. It was very heavy," said an eyewitness who gave his name as Yussef.
The Syrian Observatory for Human Rights said war planes conducted at least eight raids on Jobar on Wednesday.
The Britain-based monitor said pro-regime forces including troops from Lebanon's Hezbollah movement were battling Syria's Al-Qaeda affiliate Al-Nusra Front in the area.
Air raids on Douma, a rebel-controlled suburb of Damascus, also killed two children, according to the Observatory.