The director-general of the Committee of the Red Cross says it is trying to reach out to the Islamic State group to help get humanitarian aid to people in areas under its control.

Yves Daccord made the comments to The Associated Press on today's start to a major gathering of the Red Cross and Red Crescent held every four years.

The conference in Geneva aims partly to reinforce humanitarian law now under threat in conflict zones like Syria, Iraq, South Sudan, Afghanistan and Yemen.

Daccord said the Red Cross is a "radically neutral" organisation trying to have "a relationship where we can do it" with the Islamic State group.

He said it's very difficult in Syria because some IS-controlled areas "are pretty off-limits for any humanitarian".