The ex-Portsmouth and Everton striker most recently played for League Two Coventry in April but departed the Sky Blues after making just three appearances.
And the 35-year-old, who debuted for the Super Eagles in 2000 while also helping them to the 2010 World Cup, will now bring down the curtain on his playing career, which included spells with Middlesbrough and Blackburn.
He told Sky Sports News: "I would like to officially announce my retirement from professional football today.
"Firstly, I would like to thank God for the career I have had. I would like to thank the entire Nigerian Football Federation and my Nigerian national team-mates for all the memorable years I had playing for the Super Eagles.
"I would also like to thank all the football clubs I played for. The managers, all club staff, owners, fellow players and my dearest family and friends who immensely supported me throughout my career.
"When I started my career at Julius Berger in Nigeria all those years ago (1997) I could only have dreamt of the success that was to follow years after.
"Also playing in England especially helped me grow as a player and as a person so much that I am now settled here. I feel the time is right for me to now focus on the next chapter in my life."