NEW YORK (Reuters) - Wachovia Corp WB.N, the fourth-largest U.S. bank, plans to cut 12 percent of jobs in its markets and investment banking operations in the second quarter, Chief Financial Officer Tom Wurtz said on Monday.

The job cuts are on top of previous cuts and would result in the elimination of 24 percent of jobs in the unit since the start of 2007, Wurtz said on a conference call.

"These markets are going to remain subdued for a longer period of time," Wurtz said. "We remain very committed to the platform and we'll continue to make investments at the appropriate time, but at this point it's the time for paring back some."

Earlier Monday, Wachovia posted a surprise $350 million (176 million pound) first-quarter loss, hurt by soaring credit costs and $1.56 billion of write-downs in its investment banking unit.

(Reporting by Jonathan Stempel, editing by Gerald E. McCormick)