Deutsche Bank on Thursday reported a sharp rise in second-quarter profit driven by unexpectedly strong investment banking revenues and lower overall taxes, but warned challenges remain.

Germany's biggest lender said net profit more than tripled to €796 million ($873.52 million) from €237 million in the same period last year, on revenue of €9.2 billion, up from €7.86 billion. Its tax rate fell to 33% from 74% a year earlier.