Ziercke told news magazine Focus: “We see clear parallels with the circumstances in Spain.” It is widely believed that the Madrid terrorist attack of March 2004 had an influence on the election in Spain, and led indirectly to the withdrawal of Spanish troops from Iraq.

Ziercke sees radical converts to Islam based in Germany as a particular threat. “They know the German infrastructure, they are socially integrated, and we have to assume that they are prepared to do anything.” According to the BKA, a few dozen German Islamists have been trained in terrorist training camps.

“Often misguided converts are the most radical,” said Ziercke, though he warned against being suspicious of all Muslim converts.

The recently-broadcast al-Qaeda videos explicitly threatening Germany have put the government’s main security departments such as the BKA, and the domestic intelligence agency the Verfassungsschutz on high alert. “The latest videos show clearly that Germany and German interests abroad are threatened,” said Verfassungsschutz president Heinz Fromm.

Fromm told the newspaper Hamburger Abendblatt the statements made by terrorist Bekkay Harrach in one of these videos strongly suggested an attack ahead of the German election.

According to statistics published in Focus, the number of Islamist-motivated crimes has risen in the past year. The BKA is currently investigating 160 cases, a significant increase on the 105 being investigated a year ago. Since September 11 2001, 61 Germans have been killed in Islamic terrorist attacks on foreign soil.