Nomura Holdings Inc., the nation's biggest brokerage, has started eliminating about 30 percent of the jobs in its European, Middle East and African investment banking division, according to a source briefed on the plans.

The cuts, started Thursday, mostly affect bankers in the advisory and industry coverage areas within the securities unit, the source said, asking not to be identified because the plans haven't been made public. Officials at Nomura declined to comment on the reductions, which were first reported by CNBC.

The cutbacks are part of the company's $1 billion cost reduction target, with almost half the savings coming from Europe. The revamp in strategy follows a four-year struggle to build a business overseas after the purchase of Lehman Brothers Holdings Inc.'s European and Asian units in 2008.

The firm last week cut a team of London proprietary traders focused on stocks, said two sources with knowledge of the matter. The group of about five was part of Nomura's Angel Lane Principal Strategies, a unit that makes wagers on markets with capital provided by the bank, according to the sources, who also declined to be identified as the cuts hadn't been announced.

Nomura will also eliminate four of its 12 investment banking jobs in Dubai, a source said Thursday.