BEIRUT (Reuters) - Syrian government and allied forces have taken the eastern town of al-Mayadeen from Islamic State, a Syrian military source said on Saturday, further weakening the militants  diminishing presence in Syria.   Al-Mayadeen, near the Iraqi border in Deir al Zor province, had become a major base for Islamic State militants as they were being driven out of their de facto Syrian capital in Raqqa city by a U.S.-backed offensive.   Over the past few months many of the individuals which the U.S.-led coalition against Islamic State has targeted have come from al-Mayadeen, coalition spokesman Ryan Dillon told Reuters.     The Syrian government campaign to take al-Mayadeen has been supported by heavy Russian air strikes. The U.S.-led coalition has also previously struck in the vicinity of the town.  Al-Mayadeen lies south of the provincial capital Deir al-Zor city, where Syrian and allied forces are also trying to oust the militants from a small pocket they still control.   The Syrian military source said the jihadists in al-Mayadeen had suffered a  collapse  in their ranks.  
Islamic State loses al-Mayadeen in eastern Syria: military source