[europe refugee migrant crisis]REUTERS/Stringer * TURKISH THREATS TO SEND MILLIONS OF SYRIAN REFUGEES TO EUROPE'S DOORSTEP IF IT IS SANCTIONED OR CONDEMNED FOR ITS MILITARY INTERVENTION IN NORTHEAST SYRIA ARE CREDIBLE, EUROPEAN AND TURKISH SECURITY OFFICIALS TOLD BUSINESS INSIDER FRIDAY. * TURKISH PRESIDENT RECEP TAYYIP ERDOGAN HAS THREATENED TO FLOOD EUROPE WITH SYRIAN REFUGEES IF EU GOVERNMENTS ARE TOO STRONG IN THEIR CONDEMNATION OF THE TURKISH MILITARY ACTION IN THE COUNTRY LAUNCHED THIS WEEK. * AN OFFICIAL WITH THE GREEK GOVERNMENT TOLD BUSINESS INSIDER THAT ERDOGAN IS NOT BLUFFING, AND THAT TURKEY COULD "SEND ABOUT 500,000 REFUGEES IMMEDIATELY." * EUROPEAN GOVERNMENTS FEAR A REPEAT OF THE 2015 MIGRANT CRISIS, WHEN OVER A MILLION MIGRANTS PUSHED INTO EUROPE FROM THE MIDDLE EAST. * VISIT BUSINESS INSIDER'S HOMEPAGE FOR MORE STORIES. Turkish threats to send millions of Syrian refugees to Europe's doorstep if sanctioned or condemned for its military intervention in northeast Syria are credible, European and Turkish security officials told Business Insider Friday. Turkish President Recep Tayyip Erdogan threatened to unload many of the estimated 3.6 million Syrian refugees currently in Turkey after European capitals responded with concern over this week's decision to send the Turkish military into Syria to push a Kurdish seperatist group off the border.SEE THE REST OF THE STORY AT BUSINESS INSIDERNOW WATCH: Violent video games are played all over the world, but mass shootings are a uniquely American problem SEE ALSO: * Saudi Arabia is admitting general tourists for the first time. Here are 20 things that could get you arrested or fined, like dabbing, carrying a Bible, or wearing shorts * Lindsey Graham threatens 'sanctions from hell' and warns Turkey against crossing a 'red line' as it readies for attack in Syria * Trump's abrupt decision to pull out of Syria was reportedly made 'instinctively' at the end of his call with Turkey's president