FILE PHOTO: German police officers control a car at a permanent checkpoint on the motorway between the Austrian and German border in Kiefersfelden, Germany July 11, 2018. REUTERS/Lisi Niesner/File Photo

BERLIN (Reuters) - Germany will extend temporary controls at its border with Austria for six months due to concerns the EU’s external frontiers are not sufficiently protected, the interior ministry said on Friday.

Germany coordinated the decision with Austria, Denmark, Sweden and Norway, a ministry spokeswoman said. The Danish government made a similar announcement on Friday, citing the threat of terrorism.

Germany and other countries in Europe’s normally controls-free Schengen zone introduced emergency border controls in 2015 after more than 1 million refugees and migrants entered Europe.

The extension, which takes effect in December, will keep the controls in place until May 11, 2019.

The aim was still to return to passport-free travel within the EU but the conditions for that did not yet exist, with a lot of migrants still entering the country illegally, the spokeswoman said.

She dismissed any suggestion that the extension had deliberately been made public two days before a key regional election in Bavaria, where Horst Seehofer’s Christian Social Union (CSU) - the sister party to Chancellor Angela Merkel’s Christian Democrats - are heading for their worst showing in over 60 years.

The CSU is keen to be seen as taking a tough line on immigration to counter the rise of the far-right Alternative for Germany (AfD) party, which is expected to enter the Bavarian parliament for the first time.