Syrian rebels have warned that they could lose their main stronghold near the capital Damascus. Government forces are making gains towards Douma and have cut off supply roads, creating a siege of the city. And the siege is affecting hundreds of thousands of civilians who are trapped inside. Al Jazeera's Zeina Khodr reports from Beirut in neighbouring Lebanon. Subscribe to our channel http://bit.ly/AJSubscribe Follow us on Twitter https://twitter.com/AJEnglish Find us on Facebook https://www.facebook.com/aljazeera Check our website: http://www.aljazeera.com/