A convicted kidnapper on prison leave forced his way into a German school in northern Greece — for the second time in three years — and took three staff members hostage for an hour Wednesday before releasing them unharmed, police said.

Hundreds of primary and high-school students were evacuated from the school in the port city of Thessaloniki, and no one was hurt, police said.

The armed kidnapper, identified as 55-year-old Constantinos Arabadzis, was still holed up in the school after releasing its German director, a German teacher and the Greek financial director.

Arabadzis was negotiating with police after initially demanding a cash payment, police said. They said Arabadzis claimed to be carrying a bag packed with arms and explosives, but the claim could not be verified. No shots had been fired.

Arabadzis is serving a 19-year sentence imposed in 1995 for kidnapping two German bank officials.

During an earlier prison leave in 2006 he detained two officials from the same school in Thessaloniki for four hours. At the time he was carrying a bag containing guns, hand grenades and explosives.

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