The suspect has been described by British police as tan, with dark unkempt hair, unshaven and having a distinct body odor, the Daily Telegraph reported.
He allegedly sexually assaulted five girls between seven and 10-years-old from 2004 to 2007. The suspect allegedly broke into hotel rooms of British vacationers in the Algarve region of Portugal.
McCann went missing from her family's holiday apartment in Praia da Luz on May 3, 2007. She was three years old.
"We need to establish the identity of this man. These offenses are very serious and no one has been charged in connection with them. We also need to eliminate this man from our inquiries and ascertain whether these offenses are linked to Madeleine's disappearance," said Detective Chief Inspector Andy Redwood. "If you have been a victim of a similar crime please come forward even if you reported the incident to police in Portugal, or anywhere else, please do not assume we have been made aware of it.
"While some of these offenses have been in the public domain before, following our appeal in October three more were reported to us as a direct result of that appeal. One of those reports we believe is the first in the potential series," Redwood said.