A new Internal Revenue Service unit set up to catch rich tax cheats hiding their wealth in complex business entities is rapidly taking shape with the hiring of hundreds of employees.

The IRS high wealth unit, part of a broader effort to combat international tax evasion, is focusing on "the entire web of business entities controlled by a high wealth individual," IRS Commissioner Doug Shulman told a tax conference this week.

Another IRS official told Reuters "hundreds" of people have already been hired to staff the new unit, including some from within the agency.