DAMASCUS, Feb. 21 (Xinhua) -- The rebels in Syrian Damascus' Eastern Ghouta region didn't respond to calls for a cessation of hostilities and laying down arms, the Syria-based Russian Reconciliation Center said Wednesday.

In a statement, the Russian center said the "the armed men in Ghouta haven't responded to the repeated calls of our military personnels to lay down weapons and start negotiating."

"We haven't received any response from the armed groups in that area," the statement said, adding that the rebels in Eastern Ghouta are preventing the civilians from leaving.

The statement warned of the deteriorating humanitarian situation in Eastern Ghouta.

The rebel-held Eastern Ghouta has been under a heavy government forces' shelling since Sunday evening, as part of the first stage of the Syrian forces offensive to end the presence of the ultra-radical rebel groups, including al-Qaida-linked ones, in that region.

The Syrian Observatory for Human Rights said as many as 3,000 airstrikes and artillery shelling targeted Eastern Ghouta over the past four days.

The UK-based watchdog group said a total of 310 people have been killed and over 1,550 others wounded by the shelling on Eastern Ghouta over the past few days.

The oppositional monitor said six medical centers and hospitals have gone out of service as a result.

Meanwhile, the rebels in Eastern Ghouta have rained down Damascus with tens of mortar shells, leaving many people killed or wounded.

The rebel mortar shelling nearly paralyzed the life in the eastern neighborhoods of Damascus close to Eastern Ghouta.

That sprawling region, which constitutes of several towns and villages, is the only threat to the capital Damascus now that the army cleaned the vicinity of the capital from other directions from the rebel groups.