The 19-year-old was accused of "planning a right-wing extremist attack on the synagogue in Halle", the local state prosecutor's office said in a statement.
In October 2019, a neo-Nazi tried to storm the synagogue in the eastern German city on the Jewish holiday of Yom Kippur. He was unable to force his way inside and turned his fury on bystanders, fatally shooting two people.
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The teenaged suspect was not thought to have fixed a date for his attack but had recently procured a rifle, prosecutors said.
He is said to have repeatedly declared his intention to carry out the attack in a chat group on the Telegram messaging app between July and February this year.
The suspect was arrested on February 14th in Switzerland, where he was living at the time, and extradited to Germany on April 22nd.
German prosecutors accused the teen of "preparing a serious act of violence endangering the state in conjunction with the illegal possession of a firearm".
The suspect, who previously lived in Halle, "denies having seriously pursued the attack plans", prosecutors said, adding that the investigation was ongoing.
Germany has seen a growing number of far-right and neo-Nazi attacks in recent years.
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