By Aziz El Yaakoubi RABAT (Reuters) - Morocco has put its security services on high alert after intelligence reports revealed a "serious terror threat" from Islamist militants returning home after fighting in Iraq and Syria, the government said. Hundreds of fighters from Morocco and other Maghreb states like Tunisia and Algeria have joined Islamist-dominated fighters in Syria's civil war and the insurgency in Iraq, and North African governments fear they will perpetrate attacks once they return. "The threats are linked to the increasing numbers of Moroccans belonging to organizations in Syria and Iraq," said a statement issued after the weekly cabinet meeting. "Many of these fighters, including some who are leading those organizations, don't hide their willingness to perpetrate terrorist attacks against our country." An al Qaeda offshoot now calling itself the Islamic State has proclaimed a "caliphate" on territory it has seized in Iraq and Syria after a lightning advance last month.