BERLIN (Reuters) - Germany has extended temporary passport controls on its border with Austria and for flights coming from Greece for six more months amid continuing concerns about attacks and illegal immigration, the Interior Ministry said on Thursday. The European Commission last month offered initial backing to a Franco-German proposal to allow more permanent border checks within the bloc s Schengen free-travel zone. Germany notified the European Commission, the Council of the European Union, the President of the European Parliament and the interior ministers of the EU-Schengen states about its decision in a letter on Wednesday. The commission allowed Germany to control its border with Austria in 2015 after a surge of refugees and migrants began arriving in western Europe. The temporary permission was due to expire on Nov. 11. Immigration will be a key issue in coalition talks by Chancellor Angela Merkel s conservatives, the pro-business Free Democrats and the environmentalist Greens.  Interior Minister Thomas de Maiziere justified Germany s move given continued security concerns, and said a complete return to free travel within the Schengen area was contingent on an improvement in the overall situation. Germany was hit by five Islamist attacks in 2016, including one in December on a Berlin Christmas market that killed 12 people.  We are working hard on this, all member states, the EU Commission and the EU Council, but there is still a long way to go,  de Maiziere said in a statement. Border controls also apply to flights to Germany from Greece, which was the gateway for thousands of migrants from Iraq and Syria. Ministry data on Wednesday showed that 140,000 asylum seekers have registered in Germany since the beginning of 2017. 