Ozuruonye Juliet Kalu was seized from her car on February 27 as she traveled to her home in Abia state. Reports said the kidnappers demanded some three million Naira ($40,000, 35,000 euros) for her release.
But it was not known whether the money was paid, Abia state police spokesman Godfrey Ogbona told AFP.
“She was released around midnight (2300 GMT) of Monday and she has been reunited with her people,” he said.
“Circumstances surrounding her release has not been disclosed to me for now.
“But we are still investigating the incident in a bid towards ensuring that those who carried out the act are arrested and brought to book.”
Nigeria’s Sporting Life publication quoted the 21-year-old footballer as saying the kidnappers initially asked for three million Naira in payment, then upped the demand to 15 million.
“We waited the whole night, we did not see her. The next morning they called again (saying) that they want more money, that the money was (being) given to another person,” he added.
“Now they are asking for the ransom of N15 million.”
Kalu made a breakthrough into Nigeria’s national side in October last year, shortly after joining French Ligue 1 side Bordeaux from Belgian outfit Gent.
Kidnapping is commonplace in southern Nigeria and the family members of prominent, wealthy individuals are regularly targeted. Most are released within days after the money is paid.