DAMASCUS, Feb. 19 (Xinhua) -- Intense shelling and airstrikes targeted the rebel-held Eastern Ghouta region east of the capital Damascus on Monday, as a prelude to a wide-scale offensive by the Syrian army on that key rebel bastion.

The Syrian Observatory for Human Rights said tens of people were either killed or wounded in the shelling that targeted several areas in Eastern Ghouta region.

Meanwhile, the people in Damascus have been hearing the sporadic sound of shelling reverberating across the city.

The government shelling is a prelude to a wide-scale military offensive against various rebel groups in Eastern Ghouta, the last remaining threat to the capital Damascus.

Meanwhile, pro-government media outlets said many people were wounded when mortar shells fired from the rebels in Eastern Ghouta slammed several neighborhoods east of Damascus.

A medical source told Xinhua that five children were wounded and taken to the French Hospital in the Qassa area east of Damascus when a mortar shell struck nearby.

The military operation in Eastern Ghouta would help in securing the capital Damascus, as that region is a key bastion of several rebel groups, including al-Qaida-linked ones.

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, prompting the UN to send several appeals for reaching a one-month cessation of hostilities to allow for the entry of relief aid to affected civilians, as that region is home to 400,000 people.

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.