An aerial view of the historic city of Palmyra, in Homs Governorate, Syria, is seen in this still image taken from a drone video courtesy of Rossiya 24, made available to Reuters on March 28, 2016. (Reuters)

An aerial view of the historic city of Palmyra, in Homs Governorate, Syria, is seen in this still image taken from a drone video courtesy of Rossiya 24, made available to Reuters on March 28, 2016. (Reuters)

An aerial view of the historic city of Palmyra, in Homs Goveronorate, Syria, is seen in this still image taken from a drone video courtesy of Rossiya 24, made available to Reuters on March 28, 2016. (Reuters)

An aerial view of the historic city of Palmyra, in Homs Goveronorate, Syria, is seen in this still image taken from a drone video courtesy of Rossiya 24, made available to Reuters on March 28, 2016. (Reuters)

An aerial view of the historic city of Palmyra, in Homs Governorate, Syria, is seen in this still image taken from a drone video courtesy of Rossiya 24, made available to Reuters on March 28, 2016. (Reuters)

A general view inside the historic city of Palmyra, in Homs Governorate in this handout picture provided by SANA on March 27, 2016. (Reuters)