Massive security precautions are in place in the German city of Frankfurt for the most important terrorism trial since the 11 September attacks. Five men suspected of links to Osama Bin Laden's al-Qaeda network are due to go on trial on Tuesday. But no direct connection has been established with the attacks on the United States. Four of the five are accused of plotting to bomb the Christmas market in the eastern French city of Strasbourg in December 2000. The five, who are of Algerian descent, are also charged with belonging to a terrorist group. The prosecution alleges they trained in camps in Afghanistan from 1998. Three of the accused were based in London before joining the others in Germany. The country became a focus of investigation into al-Qaeda cells after it emerged that three of the hijackers involved in the 11 September attacks had studied in the northern city of Hamburg.