Rifaat has been ordered to remain in France except for travel to Britain for medical treatment, said Sherpa, an activist group representing the victims of financial crime.
He was forced into exile in the 1980s for trying to overthrow his older brother, the late Syrian dictator Hafez al-Assad.
French investigators have told AFP that since then Rifaat has divided his time between homes in Paris, London and the southern Spanish resort city of Marbella.
The investigation into Rifaat's finances was triggered by Sherpa, which claims the fortune was stolen during his time at the heart of the Syrian regime.
Sherpa on Tuesday hailed "this advance in the judicial investigations involving one of the principal former dignitaries of the Syrian regime".
The Assad family claims Rifaat's fortune was the result of gifts from wealthy Saudi supporters, including former king Abdullah, with whom he shared a love of horse-racing.
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He was forced into exile in the 1980s for trying to overthrow his older brother, the late Syrian dictator Hafez al-Assad.
French investigators have told AFP that since then Rifaat has divided his time between homes in Paris, London and the southern Spanish resort city of Marbella.
The investigation into Rifaat's finances was triggered by Sherpa, which claims the fortune was stolen during his time at the heart of the Syrian regime.
Sherpa on Tuesday hailed "this advance in the judicial investigations involving one of the principal former dignitaries of the Syrian regime".
The Assad family claims Rifaat's fortune was the result of gifts from wealthy Saudi supporters, including former king Abdullah, with whom he shared a love of horse-racing.
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