Syrian rebels have taken control of areas close to Damascus, where intense fighting has effectively shut down the country's main international airport to anything but military flights.
Al Jazeera's Ahmed Zaidan, reporting from inside the Syrian capital, said anti-government Free Syrian Army (FSA) fighters extended their hold over the eastern half of Ghouta on Saturday, as heavy fighting raged in several areas in and around Damascus.
Ghouta is an agricultural belt surrounding Damascus to the south and east.
"The airport in Damascus has been effectively paralysed [for civilian flights] since two to three months. Most Syrian officials who want to travel have been forced to fly from Beirut," our correspondent said.
"Most of air traffic in Damascus comes from military flights. The only civilian flights landing there are doing so at high risk because the fighting there is very close.
"Senior FSA officials have told us that Iranian planes land in Damascus every two to three days, allegedly to bring arms and ammunition for the forces of President Bashar al-Assad."
The Syrian Revolution General Commission - an activist network on the ground in Syria - reported regime troop reinforcements being deployed in Daraya, a suburb south of Damascus.
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It reported "five tanks and three trucks accompanied by several cars and buses carrying soldiers from the Mazzeh military airport" heading towards the area, where government forces have for months been trying to establish control.
While government forces shelled parts of Damascus overnight, fighting also raged in the northern city of Aleppo, the Syrian Observatory for Human Rights (SOHR) said on Saturday.
The UK-based activist group said government shelling continued on Saturday and also affected the Yarmouk refugee camp for Palestinians along with the Jubar, Barzeh and Qaboon neighbourhoods of Damascus.
The shelling was particularly fierce in Barzeh, the group said, adding that snipers were deployed in the district as residents were reported fleeing the area.
The SOHR also reported at least 12 rebels killed in Aleppo amid clashes with regime troops near the international airport.
Meanwhile, in the eastern city of Deir az-Zor, the SOHR reported heavy fighting in the Huweika district and a car bomb blast near a building housing regime forces.
There were no immediate details on casualties in the explosion.
It said rebel forces control approximately 30 percent of the strategic town, which is located near oil fields and close to the Iraqi border.
The SOHR, which collects information from a network of representatives and medics on the ground in Syria, put the death toll for Friday at 216 people, one of the highest figures in recent weeks.
On Saturday, UNRWA, the UN agency which helps Palestinian refugees, said a member of its teaching staff had been killed in the Khan Eshieh camp, southwest of Damascus.
Nasri Khalil Hasan was killed by shrapnel that hit him as he fled his home under artillery fire, UNRWA said, adding that Hasan was the sixth member of its staff in Syria to be killed in the conflict.