A police vehicle stands in front of a residential building as an anti-terror operation is taking place in Germany today

Police in Germany have stormed 13 buildings across the country after reports ISIS terrorists were planning an imminent attack.

Anti-terror raids were launched on houses in Thuringia, Hamburg, North Rhine-Westphalia, Saxony and Bavaria as officers believed the threat was credible.

Armed police accompanied by sniffer dogs conducted the raids after being sent to look for weapons and explosives.

The operation came as part of an investigation into a 28-year-old Russian citizen of Chechen background suspected of intending to join the fighting in Syria on behalf of ISIS.

The investigation later developed into a probe of 13 further individuals, 10 men and three women, suspected of financing extremist activity.

Police said all were people of Chechen ethnicity with Russian citizenship seeking asylum in Germany, and whose status has not yet been decided.

Police said there was no concrete danger of an imminent attack. The statement did not say whether anyone was arrested.

Germany is on high terror alert after a wave of attacks this year, heaping pressure on chancellor Angela Merkel's open-door immigration policy.

A bloody week of violence that rocked Germany began on July 18 when Pakistani teenager Riaz Khan Ahmadzai, 17, posing as an Afghan refugee, hacked at passengers on a train in Wurzburg with an axe, wounding five. He was shot dead by police.

Police in Germany have stormed 13 buildings across the country after reports ISIS terrorists were planning an imminent attack (file pic)

Four days later mentally unstable German-Iranian teenager Ali Sonboly shot nine people dead during a rampage through a shopping centre in Munich before taking his own life.

Two days later a Syrian refugee, 21, hacked a pregnant woman to death in Reutlingen and on the same night Mohammed Daleel, 27, injured 12 people when he detonated a rucksack packed with metal shards and screws.