The investigation by the UN Office of Internal Oversight Services is the result of a probe into contracts in the UN peacekeeping department, which is fielding some 85,000 troops, police and civilians around the world.
Four of the suspended managers are in UN Procurement Services and four were recalled from peacekeeping missions, UN spokesman Stephane Dujarric said.
"Placing these eight staff members on special leave is an administrative, not disciplinary, measure," Mr Dujarric said.
"Staff members on administrative leave who are not the subject of any action will be returned to their posts as expeditiously as possible."
Red flags
The suspension apparently deals with those in charge of projects or contracts where irregularities were discovered in the audit, which one official said raised "red flags".
Christopher Burnham, the UN undersecretary-general for management, called the action "an indication that we have a vigorous ongoing and expanding investigation".
Mr Burnham, an American, ordered a review by the Swiss firm Deloitte and Touche after a purchasing officer, Alexander Yakovlev, pleaded guilty in US federal court in August to wire fraud and money laundering.
A UN-appointed commission investigating the now defunct oil-for-food program had accused Mr Yakovlev of pocketing more than $A1.26 million in illegal payments from companies seeking UN contracts.
The commission was headed by former US Federal Reserve Chairman Paul Volcker.
June deadline
Mr Burnham last month told a news conference that Deloitte and Touche would undertake a "forensic audit", expected to be completed in June that would also survey five years of peacekeeping contracts.
UN Procurement Services approves the purchase of goods and services for the United Nations. It oversaw $A1.82 billion in contracts for 2004.
The United Nations has previously stripped managers of their responsibility while investigations were going on.
After Mr Yakovlev pleaded guilty, UN Secretary-General Kofi Annan transferred responsibility for procurement to the UN controller's office.
Deloitte and Touche said in a report in December purchasing was vulnerable to fraud and corruption.
It cited a lack of urgency in reporting wrong-doing, virtually nonexistent ethics training, and out-of-date computer systems that prevented a systematic oversight of spending.