Two helicopters crashed near Berlin's Olympic Stadium during a federal police exercise, German authorities said. One pilot was reported to have died in the accident and several others were injured. Police have launched an investigation.
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The announcement came a day after a famine was declared in two areas of South Sudan following three years of civil war and severe inflation.
It is unclear what their alleged plans were.
Anti-terror police are currently questioning the men who were arrested at three separate locations in France.