Reports in Italy said the second part of the deal could see Napoli's Guinea midfielder Amadou Diawara moving in the other direction for a 20-million-euro fee.

Manolas, 28, is expected to form a formidable central defensive partnership with rugged Senegal international Kalidou Koulibaly.

The Greek, who signed a five-year contract, has risen to become one of the best central defenders in Serie A since he moved to Roma in 2014 from Greek side Olympiakos.