King Abdullah of Saudi Arabia has warned that terrorist groups will attack Europe and the United States

The king of Saudi Arabia has warned that terrorist groups will attack Europe and the United States unless they are faced with collective "power and speed" from the international community.

King Abdullah's comments come as the Islamic State group has seized wide areas of land across Syria and Iraq.

While not mentioning any terrorist groups by name, he said that he is "certain that after a month they will reach Europe and, after another month, America".

The king's comments appeared aimed at drawing Washington and Nato forces into a wider fight against extremists in the region.

Saudi Arabia has backed rebels fighting in Syria, but is concerned that extremists there could turn their weapons on the kingdom.

State media carried the king's comments to foreign ambassadors.