Islamic State's caliphate has been all but destroyed over the past two years, remaining only in Albu Kamal in Syria and Rawa in Iraq, in a few neighbouring towns and patches of desert, and some isolated pockets elsewhere.

However, it still has a territorial presence in Libya and other countries and many governments expect it to remain a threat even after it loses its self-proclaimed caliphate.

The Syrian army, alongside its Lebanese military ally Hezbollah and other Shia militias, and backed by Iran and Russia, have seized swathes of central and eastern Syria in an advance against Islamic State this year.

A US-backed international coalition has supported a rival campaign in Syria by Kurdish and Arab militias that have pushed Islamic State from much of the country's north and east.

In Iraq, Islamic State firmly controls only the small village of Rawa after the coalition helped the army and Iran-backed Iraqi forces fight it throughout the country.