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CHICAGO-Omnicom Group Inc. has increased its space at Michigan Plaza by 36%, signing a 90,000-sf renewal with Loeb Partners Realty. The New York-based tenant, whose subsidiaries include OMD Worldwide, Porter Novelli public relations and GMR Marketing, has been a tenant since 1999 at the two-building, 1.9-million-sf East Loop office complex at 205 and 225 N. Michigan Ave.

The 24,000 sf of new space will allow Omnicom Group to relocate the Ketchum Directory Advertising Inc. public relations and Critical Mass internet marketing groups to Michigan Plaza. Although terms were not disclosed, published asking lease rates at the 25-story and 44-story buildings start at $26 per sf. The deal reduces vacancy at Michigan Plaza to 8%

MB Real Estate managing director Mark A. Buth represented Loeb Partners Realty, which paid $266.3 million for the property in 2005, in negotiations with Lee Feld of WF Realty LLC.