Police said there were no signs of an imminent attack by militants in Germany, after a news magazine reported that a plot existed to attack the Reichstag parliament building.

The comments played down the report by weekly Der Spiegel, which said Germany's decision to step up security measures this week had been prompted by the discovery of militant plans to break into the Reichstag parliament building and shoot hostages.

'We have concrete details of suspects, but no concrete details that an attack will be carried out at a specific time and place,' the head of Germany's BKA Federal Crime Office, Joerg Ziercke, told Reuters.   

Der Spiegel, citing security officials, said a jihadist living abroad had informed them in recent telephone calls of a plan for armed militants to enter the 19th century building in central Berlin and open fire. It said police considered the information credible.   

The information, the magazine said, had prompted officials to announce on Wednesday they were raising security, especially at public places including airports and train stations.   

Interior Minister Thomas de Maiziere said on Thursday authorities were on guard against threats of an armed attack of the kind that killed 166 in the Indian city of Mumbai in 2008.

The Reichstag building has strong symbolic importance in Germany. An arson attack there in 1933 highlighted Nazi moves to assume complete control over Germany. The image of a Soviet soldier planting the red flag atop its ruin in 1945 marked the end of World War Two for many.   

It was formally restored as the country's legislature soon after the 1990 reunification of Germany and is visited daily by hundreds who walk around its glass dome looking down on debates.

Late on Saturday more than 100 tourists were lined up outside the building and no police were in sight.   

The jihadist, Der Spiegel reported, said the group of attackers was to be made up of six people. Two had already arrived in Berlin and another four, including a German, a Turk and a North African, were under way.   

Germany has troops in Afghanistan and has been the target of threats on Jihadist websites. 

The timing of the reported parliament plot, for February or March, differed however from de Maiziere's warnings that attacks were planned sometime before the end of November. - Reuters