German authorities have released all four suspected Islamists arrested on suspicion of having plotted a "state-endangering act" ahead of festivities to celebrate the country's reunification.

Police announced Sunday that three men had been arrested near the western German city of Bonn, where around 100,000 were expected to take part in German Unity Day celebrations attended by both Chancellor Angela Merkel and President Christian Wulff. A further suspect was taken into custody in Offenbach in the central state of Hesse.

Authorities had received information that the men, whom they described as being "from the Islamist scene," had illegally obtained weapons ahead of the events. But police found "no weapons or other dangerous objects" during their searches.

"There is neither evidence that the accused had links to terrorist groups nor that there were concrete preparations for an attack," said a spokesman for the Federal Prosecutor's Office.

As a result, the Offenbach suspect was released after being held for just a few hours on Saturday. The three Bonn men, who were also taken into police custody on Saturday, were released late on Sunday.

The Prosecutor's Office, which handles domestic terrorist threats and has said it is tracking around 200 potential Islamist terrorists in Germany, did not see sufficient grounds for it to take over the investigation from the local police force.

Authorities also said they did not know of any concrete threats to the festivities, which are continuing through Monday October 3, the 21st anniversary of German reunification.

Prior to the 10th anniversary of the September 11 attacks on the United States, police in Berlin arrested two suspected terrorists, who are still being held for questioning.

Author: David Levitz, Chuck Penfold (AFP, AP, dpa)

Editor: Michael Lawton