Europe's REAL crisis: Terror warning as as 6,000 refugees arrive on Lesbos in just three days with no end to the human tide of misery <br />Europol said there could be 5,000 jihadis in the EU and the Continent is facing its biggest security crisis in ten years <br />It said at least 4,700 EU citizens had been recorded as fighting overseas in countries such as Syria and Iraq <br />Security officials fear many could have slipped back into the EU and British officials suspect 400 are in the UK
