At least 37 civilians were killed Wednesday in Syrian government air strikes near Damascus, while at least 13 people died as rebels fired a barrage of rockets into the capital, a monitor said.
The Syrian Observatory for Human Rights said at least four children were among the dead in regime strikes on the rebel-held Eastern Ghouta region, where some 120 people were also wounded.
The death toll was likely to rise further, it said.
The air raids hit the towns of Douma, Saqba, Kafr Batna and Hammouriyeh in the rebel stronghold.
An AFP photographer in Douma saw more than a dozen bodies in makeshift plastic shrouds in a field hospital where medical workers struggled to aid the wounded.
Elsewhere, he also saw two plastic shrouds opened at the top to reveal the faces of two children, their skin yellow and blood-speckled.
Inside a clinic, a young boy wept and hugged his legs -- one roughly bandaged -- as he sat on a blood-smeared floor next to other injured residents.
The strikes came as rebels fired dozens of rockets into Damascus.
The Observatory, without specifying whether the raids or the Damascus attack came first, said at least 13 people, among them 10 civilians, were killed as a barrage of more than 50 rockets slammed into the capital.
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It said another 60 people were wounded.
Syria's antiquities director Mamoun Abdulkarim told AFP by telephone from Damascus that rockets had struck near the capital's museum and historic citadel.
"The deputy director in charge of our mosaic pieces, Qassem Yahya, was killed. He was 38," Abdulkarim said.
"Another rocket fell by the museum's entrance and a passerby was killed," the director added.
Syria's state news agency SANA, citing a police source, put the toll at five dead with 55 injured, "most of them children and women."
Rebels often fire into the capital from rear bases on its outskirts, including at times barrages of hundreds of missiles.
Rights groups have condemned indiscriminate rebel rocket fire as amounting to war crimes.
The government regularly carries out air strikes against rebel-held areas on the outskirts of Damascus, particularly Eastern Ghouta, which is also under regime siege.
On Wednesday, Amnesty International accused the government of war crimes against Eastern Ghouta residents, saying heavy aerial bombardment was compounding misery created by the blockade.
More than 240,000 people have been killed in Syria's conflict since it broke out in March 2011, and millions have been forced to flee their homes.