Citigroup's investment bank is planning to lay off about 10 percent of its global staff, or roughly 6,500 people, beginning today. Separately, the Financial Times reports Goldman Sachs is expected to reduce headcount at its investment bank by a similar proportion over the summer.

Citigroup has let go at least 9,000 of its total 350,000 employees as of March 31, the Journal says, adding the cuts expected this week "are unusual in their scope and severity." M&A bankers, who haven't suffered as many casualties as colleagues in other units so far, may see "especially sharp cuts," the newspaper reports. Entire trading desks may go, and many senior managing directors may lose their jobs. However, some emerging markets and the bank's transactions-services unit may avoid much of the pain.

Citigroup has reported about $15 billion in losses in the last two quarters, and is expected to report billions more when it announces second-quarter results, the Journal notes.

At Goldman, which reported second-quarter earnings of nearly $2.1 billion, the FT says the cuts are noteworthy because the bank's "heightened pessimism about its need to retain its more experienced staff during the rest of 2008 could prove a pretext for other banks to wield the axe with greater force."