Hundreds of thousands of Syrians are being intentionally denied food, water and medicine.
According to the UN, almost 500,000 people are living under siege.
They are besieged by forces aligned with the regime in Damascus, or by other groups. They are among the 4.6 million civilians living in "hard-to-reach" locations, according to a UN estimate.
Political leaders from across the world gathered in London for a donor conference to help the victims of Syria's war and pledged $10bn to help the Syrians.
Some of the money will assist Syrians who have fled to neighbouring countries and to Europe.
But will money allocated to help those in need inside the country reach them there?
And is Bashar Al Assad's regime, in particular, using siege as a means of warfare in the towns and villages of Syria?
Presenter: Peter Dobbie
Kevin Jon Heller - professor of criminal law at the University of London's School of Oriental and African Studies
Bissan Fakih - senior campaigner, The Syria Campaign advocacy group
Julien Barnes-Dacey - senior policy fellow at the European Council on Foreign Relations
Source: Al Jazeera