Translate to French:

It was in 1959, while Rwanda was still under United Nations trusteeship, that the first acts of genocide against Tutsis took place there, leading to the first mass refugee problem on the African continent.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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C'est en 1959, alors que le Rwanda était encore sous la tutelle de l'Organisation des Nations Unies, que les premiers actes de génocide contre les Tutsis y ont été commis, créant le premier problème massif de réfugiés sur le continent africain.