Deutsche Bank appears set to buy a stake of about 75 per cent in the Luxembourg-based private banking and investment group Sal Oppenheim for about €1 billion ($1.5 billion) as soon as next week, Reuters said, citing an unnamed source.

Deutsche is looking at all Sal Oppenheim assets apart from the investment bank although it remains unclear whether the bank would also buy a private equity fund controlled by Sal Oppenheim's owners, the news agency said.

Details of the deal are still under negotiation.

The outlines of a deal could be presented around the same time as Deutsche Bank earnings, due to be released on 29 October.

Sal Oppenheim's family owners are selling parts of the business after the bank posted its first post-war loss last year. Deutsche has already stepped in to provide €650 million euros in loans to the firm.

Separately, Australia's Macquarie Group is close to clinching a deal to buy Sal Oppenheim's investment banking arm, other sources close to the matter told the news service.

Sal Oppenheim had entered exclusive talks to sell off its investment banking business with Macquarie, WealthBriefing learned earlier this month.