The iconic skyscraper, at 30 St Mary Axe, is known as the Gherkin because of its distinctive shape.
According to the Financial Times, the group - headed by billionaire Brazilian businessman Joseph Safra - paid £726m for the 180m high Norman Foster-designed tower.
The building was put up for sale earlier this year with a guide price of £650m.
The Gherkin is the second tallest tower in the City of London and the sixth tallest in London.
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