(Adds comments from German officials 7-9)

By Alexandra Zawadil and Boris Groendahl

VIENNA, Nov 20 (Reuters) - An Islamist group calling itself the "Global Islamic Media Front" has sent a video demanding Germany and Austria withdraw their troops from Afghanistan, Austria's interior ministry said on Tuesday.

The video, published on the web site of Austrian daily newspaper Oesterreich, also demands the release of two Austrians arrested in Vienna in September on allegations they helped produce a similar video message published in March.

"The German soldiers still occupy Afghanistan and we repeat our call from the last video that Germany withdraw their troops from Afghanistan," the mostly German-language video said. "This only serves your own security in your country.

"The same applies to Austria too. The mujahideen have spared you so far, therefore the number of dead soldiers is not particularly high. But this will now change..."

Germany has some 3,000 troops in Afghanistan as part of the NATO-led International Security Assistance Force (ISAF) mission. Three Austrian soldiers serve as part of ISAF in Kabul.

"We address the Austrian government: We demand the brothers and sisters arrested in Vienna be released immediately, or else you will regret that you dared to lock up Muslims in your prisons," it says.

German Interior Minister Wolfgang Schaeuble said authorities were taking the video seriously, but said Germany was not scared by the threats.

"There is no sense in letting ourselves feel blackmailed," he told a police conference in Wiesbaden, near Frankfurt.

Joerg Ziercke, the head of Germany's BKA federal police, told the same conference that the video showed scenes already used in the March video, but said the new material targeted both politicians and Islamic groups.

A spokesman for the Austrian interior ministry said it received the video a few days ago and was investigating its origins.

"There is no identifiable, immediate threat, but nevertheless such a message needs to be taken seriously," the ministry's Rudolf Gollia said. Austria has not raised security levels for government members. (Additional reporting by Sylvia Westall in Berlin; Writing by Boris Groendahl; Editing by Caroline Drees)

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