Islamic State conflict: Fighters near UNESCO World Heritage site at Palmyra

Islamic State militants have moved to within a few miles of one of the world's oldest and most important archaeological cities, Palmyra, in the latest stage of their campaign in Syria.

It is thought that key Syrian military bases are their primary targets but a UN cultural official has expressed alarm at the risk to a UNESCO World Heritage site in the area.

The militants have a record of destroying what they describe as "idolatrous" sites in Iraq and Syria, filming their work as part of their propaganda videos.

World affairs correspondent Richard Galpin reports.