Police arrested a German man on suspicion of leaving an orange backpack filled with fake bombs at an annual street parade in Zurich, Switzerland, they said on Monday.

Swiss police said they had detained the 31-year-old at his home on Sunday after "complex and intense investigations." Police said he lived in the Aargau region of Switzerland, but did not provide any additional information on the suspect.

A police spokesperson said they had not identified a "discernible ideological background to this deed." They added that they had not found an explanation for why the bomb had been built in the first place.

Around 850,000 people attended the parade on Saturday, which celebrates universal freedoms and world peace.

Read more: Suspected neo-Nazis behind bomb threats across Germany: reports

Forensics experts at the scene said the fake bombs looked very real — police confirmed they had released a 35-year-old, who was previously detained for questioning.

City halls, political headquarters and public transport have recently been targeted with bomb threats in Germany. This arrest comes a month after police evacuated the headquarters of the German Left party in Berlin over a bomb threat.

jns/aw (AP, dpa)

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