The US attorney general has called on European governments to be stronger in preventing their own citizens from joining the fighting in Syria.  Eric Holder said the Syrian conflict had turned into ‘a cradle of violent extremism’ that could threaten Western countries when fighters return home. He made his remarks during a speech to Norwegian diplomats in Oslo.  US officials believe there are about 7,000 foreign fighters in Syria, including dozens of Americans.  In May, a 22-year-old man from Florida carried out a suicide bombing mission in the country and a Colorado woman was arrested at an airport in April after US officials said she was intent on providing support to the militant group ISIS  in Syria.  In the speech, Mr Holder called on European governments to make it illegal to plan or support terrorist plots, to catch potential fighters before they leave for Syria through undercover plots and share information about those who have travelled to Syria to fight, including through Interpol.