Fadiga opened the scoring for the Teranga Lions before Diouf converted a penalty just before the break.
Abdoulaye Diagne-Faye grabbed the third Senegal goal early in the second half, before Southampton's Henri Camara, Moussa N'Diaye and a second from Diouf completed the rout in front of over 60,000 fans in the Senegal capital, Dakar.
Elsewhere, Wanderers' Jussi Jaaskelainen kept goal for the Finland side that lost 4-3 to Czech Republic in their World Cup qualifier in Teplice.