Having struggled recently to make money from overseas trading, Nomura Holdings Inc. will shut a loss-making proprietary unit in London and four of the group's top managers may leave, according to people with knowledge of the matter.

The group, run by Jonathan Och, employed 10 money managers and used capital provided by Nomura to bet on stocks, bonds, currencies and distressed debt, the people said, asking not to be identified because the information is private. While the people didn't say whether Och remains at Nomura, four senior portfolio managers, Stephen Kirkham, Jonathan Fittall, Dominic Hubble and Guy Joseph, are close to exiting, they said.

The move follows a multiple-year retreat by global banks from proprietary trading amid a wave of new restrictions imposed since the financial crisis. Deposit-taking lenders in the U.S. are restricted from the practice under the Volcker Rule, while lenders across Europe have to wall off the operations into separate units.