(Reuters) - Here is a timeline of plots in Europe linked to German-based Islamist militant groups:
June 2005 - An appeals court upholds acquittal of Moroccan Abdelghani Mzoudi, accused of complicity in September 11 attacks and belonging to a terrorist group. He was expelled.
October 2005 - Four Arab men found guilty of planning to bomb Jewish targets in Germany on orders of militant leader Abu Musab al-Zarqawi receive sentences of between five and eight years. They had planned attacks on two Jewish-owned Duesseldorf discos and a Berlin community centre.
January 2007 - Germany’s highest court rejects appeal by Moroccan Mounir El Motassadeq, friend of September 11 hijackers, who was sentenced to 15 years in prison in November 2006 for being an accessory to mass murder.
December 2008 - Court in Duesseldorf convicts Youssef al-Haj Deeb, a Lebanese, of attempted murder of an undefined number of people. Prosecutors said the planned attacks in western Germany could have caused up to 75 casualties. Haj Deeb and his accomplice Jihad Hamad boarded two trains in Cologne, one headed for Koblenz, one for Dortmund, in July 2006 with suitcases containing propane gas containers and crude detonators.
March 2010 - Duesseldorf court convicts four militants who admitted planning “a monstrous bloodbath” with car bomb attacks on U.S. targets in Germany. They were known as the “Sauerland group” after the area of western Germany where they were caught.
August 2010 - Police shut Taiba mosque, previously known as Al-Quds Mosque. The mosque was once frequented by Mohammed Atta, leader of the group that carried out September 11 attacks.
September 2010 - A German Islamist held by U.S. troops in Afghanistan and interrogated since July reveals details of planned attacks on targets in Europe, intelligence sources say.
— On September 4 German news weekly Der Spiegel identifies the man as German-Afghan “Ahmed S.”, of the Islamic Movement of Uzbekistan (IMU), a Central Asian militant group, who had worked on recruiting new members in Germany.
— He was subsequently identified as Ahmed Sidiqi, a German of Afghan origin among a group of 10 or 11 militants who left Hamburg for armed training in northwest Pakistan in March 2009.
October 14, 2010 - The United States warns its citizens of potential for terrorist attacks in Europe. Western security sources say the alert stems from information from a captured German Islamist about a possible al Qaeda-related plot.
March 2, 2011 - Lone gunman, enraged over the war in Afghanistan, shoots dead two U.S. airmen and wounds two others at Frankfurt airport. A prosecutor says he probably acted alone.
March 31, 2011 - Police say they detained a 25-year-old man suspected of planning a bomb attack outside a soccer stadium in the western city of Dortmund. The Federal Crime Office (BKA) said it found and defused three suspected explosive devices near the stadium used by Bundesliga side Borussia Dortmund.
April 29, 2011 - Police arrest three people in Germany suspected of being members of al Qaeda, federal prosecutors say. The three, all Moroccans, were arrested in Duesseldorf and Bochum. The ringleader, a college drop-out identified as Abdeladim El-K., is charged with planning an attack in Germany. Authorities said police seized large amounts of explosives.
May 9, 2011 - A German-Syrian man, identified only as Rami M., who confessed in a Frankfurt court to having travelled to Pakistan’s tribal regions to train with al Qaeda from 2009 to 2010, is sentenced to four years and nine months in prison.
— Rami M. gave information to intelligence services about possible attacks in the country, prosecutors also say.
July 20 - An Afghan national is arrested in Germany on suspicion of recruiting or fundraising for international militant groups Al Qaeda and the Islamic Movement of Uzbekistan, federal prosecutors say the next day.
— Identified as Omid H., he is alleged to have published articles and videos on an Islamic Internet site glorifying terrorist attacks with the intent of recruiting new members or raising money for the networks.
August 31, 2011 -A 21-year-old Kosovo Albanian man confesses to shooting dead two U.S. airmen and wounding two more at Frankfurt airport in March, telling the court he was swayed by Islamist lies and could not undo what he had done.
Reporting by David Cutler, London Editorial Reference Unit and William Maclean