The chief of the International Monetary Fund, Dominique Strauss-Kahn, is under investigation as to whether he abused his position by engaging in a sexual relationship with wife of former Argentine central bank president and his subordinate Piroska Nagy, Bloomberg reported Saturday.

There was an allegation concerning improper behavior of a personal nature on the part of the managing director, said Masood Ahmed, the IMF's director of external relations.

Strauss-Kahn began approaching Nagy about an affair in December 2007. The two exchanged e-mails about a possible intimate relationship, which commenced early this year during a conference in Europe.

Hungarian-raised Nagy was a senior official in the IMF's Africa department at that time.

In a statement, Strauss-Kahn said the incident took place in January, as part of his private life, and denied any abuse of his position.

Strauss-Kahn has cooperated and is continuing to cooperate with the IMF's outside counsel concerning the matter, the statement reads.

The IMF has retained the firm of Morgan, Lewis & Bockius LLP to conduct the investigation, which is expected to be completed by the end of the month.