DAMASCUS, Feb. 20 (Xinhua) -- At least five people were killed and over 20 others wounded on Tuesday by intensified rebels' mortar attack on the capital Damascus, the state news agency SANA reported.

SANA said the rebels' shelling is ongoing, targeting several residential neighborhoods mainly east of Damascus, close to the rebel-held Eastern Ghouta countryside.

Meanwhile, the opposition activists said the Syrian warplanes and artillery are relentlessly targeting the rebel-held Eastern Ghouta region, killing tens of civilians and wounding hundreds of others.

People in the capital have been hearing the intense shelling by both sides since Sunday evening when the Syrian forces started paving the way for a wide-scale ground offensive on Eastern Ghouta by heavy fire cover.

The anticipated attack hasn't started, but the shelling and airstrikes are the preludes to the attack, amid heavy mortar attacks by the rebels against the residential areas in the capital.

The situation in the Eastern Ghouta has flared up over the past two months, when the rebels, including the al-Qaida-linked ones, unleashed a massive offensive against a key Syrian military base in the Harasta city in Eastern Ghouta.

The rebels' mortar attacks have rained down the capital Damascus, while the Syrian military's shelling and airstrikes hit several areas in Eastern Ghouta.

However, the situation has become calm over a few days before a new escalation on Sunday evening.

Syrians in the capital have for long been calling for the elimination of the rebels' mortar attacks, which, in many cases, paralyzed the lives of the people in the eastern Damascus neighborhoods.

Four key rebel groups are positioned inside Eastern Ghouta such as the Islam Army, Failaq al-Rahman, Ahrar al-Sham and the Levant Liberation Committee (LLC), otherwise known as the al-Qaida-linked Nusra Front.