Syria's conflagration - again on the doorstep of its capital.

This video purportedly shows rebels in pitched battles with government troops in a suburb of Damascus.

The footage was posted to a social media website and could not be independently verified by Reuters.

But it suggests that rebels are making headway in their efforts to reach the capital.

This video clip is said to show rebels lobbing rockets at Damascus International Airport, which sits 20km from the city centre.

Meanwhile, other footage shows what appear to government forces - and their heavy machinery - fighting back against rebels in another suburb.

Neither side has been able to gain the upper hand in the 20-month conflict that has left an estimated 40,000 people dead.