Rebel fighters in Syria say that they are aiming to seize Damascus airport, saying it's a fair target because it is being used by the Syrian military.
There has been fierce fighting in recent weeks in the countryside around Damascus, known as the Ghouta.
The city's international airport has been inaccessible or closed to civilian flights repeatedly over the past two weeks, the BBC reports.
As clashes continue there, a spokesperson for the rebel Damascus Military Council, Nabil al-Amir, has warned civilians that they approach it at "their own risk".
"The rebel brigades who have been putting the airport under siege decided yesterday that the airport is a fair target," he told the Reuters news agency. "The airport is now full of armoured vehicles and soldiers."
Meanwhile the Syrian army has reinforced positions outside two south-western suburbs of Damascus, activists say, raising fears of a ground attack.
Throughout the day the army has been shelling the suburb of Darayya, the centre of which is controlled by armed rebels.