Syria conflict: Dozens killed in heavy Damascus fighting
Heavy fighting in and around the Syrian capital Damascus has killed at least 40 people and wounded many more, state media and observers say.
The Syrian Observatory for Human Rights said at least four children were among 35 people killed in nearly 40 air raids on Thursday in a Damascus province.
At least five people were also killed in a series of rebel mortar attacks on the capital, state media report.
Rebels have vowed to avenge government attacks on the nearby town of Douma.
On Tuesday, Jaysh al-Islam (Army of Islam) leader Zahran Alloush said his group now considered Damascus a "military zone"- the latest attacks on the capital were apparently carried out by them.
The rebel group, which follows Islamist doctrine and has reportedly received support from Saudi Arabia in the past, was behind a series of rocket attacks on the Syrian capital in January, which killed seven people.
The Syrian air force attacks on the Eastern Ghouta area - about 10km (six miles) north-east of Damascus - came in response to mortar attacks in the capital earlier on Thursday.
The Syrian Observatory for Human Rights said dozens were wounded in the air strikes.
A photographer for the AFP news agency said he saw civilians streaming into a makeshift clinic, with doctors overwhelmed by their numbers. Some had to be treated on the floor.
Earlier, rebels fired a barrage of rockets and mortar shells on central Damascus. Grey smoke was seen rising above the capital, amid the wailing of ambulance sirens.
Much of the bombardment was centred on Baramkeh, home to Syria's state-run Sana news agency and Damascus University, which was forced to close.
The head of a local school told the AFP news agency that she was forced to escort pupils into a bomb shelter because of the shelling. State television said that three missiles struck near the Old City's Umayyad Mosque, one of the largest in the world.
Government forces have been regularly attacking Douma and its surrounding areas - a stronghold of Mr Alloush's group - by air raids and helicopter barrel bomb attacks. Hundreds of civilians have been killed alongside opposition fighters.
The Syrian civil war has escalated dramatically, having begun following initially peaceful protests four years ago against the government of President Bashar al-Assad, who has been in power since succeeding his father Hafez al-Assad in 2000.
United Nations figures show that over 220,000 people have been killed in the four-year conflict, which has seen the rapid emergence of numerous heavily-armed jihadist groups within Syria, including Jaysh al-Islam, Islamic State (IS) and al-Qaeda offshoot al-Nusra Front.
The UN's High Commissioner for Refugees says more than nine million Syrians have been displaced as a result of continuing fighting.
The Syrian government has carried out innumerable air strikes on rebel-held territory throughout the conflict, and has been accused by human rights organisations of killing thousands of innocent civilians in the process.