The U.S. Secretary of State John Kerry has arrived in the Iraqi capital Baghdad as Islamist militants continue to make gains in the country.

The ISIS militant group is now in control of much of Iraq's western border, after capturing three more towns in the Anbar province yesterday.

US President Barack Obama is warning that they're threatening to destabilise the whole of the Middle East region.

Chief Foreign Correspondent with the Sunday Telegraph Colin Freeman is in Baghdad - he's explained why the ISIS group is so hard for the Iraqi army to tackle: