A new United Nations report says the world is facing a challenge from foreigners traveling to fight in terror groups on an "unprecedented scale," with about 15,000 in Syria and Iraq alone.

The report by a panel of experts monitoring al Qaeda and the Taliban, the Associated Press says it obtained Friday, Oct 31 has been submitted to the UN Security Council.

The panel says fighters from more than 80 countries working with al Qaeda associates in Syria and Iraq "form the core of a new diaspora that may seed the threat for years to come."

The report adds that the increasingly sophisticated use of social media is giving the Islamic State group a "cosmopolitan" appearance.