Oasis have released their new single this week
The group's label, Sony, said the bootlegged tapes were probably made by someone with a hidden recording device.
The album, entitled Heathen Chemistry, is due for release in July, but fans have been able to download MP3 audio files of the tracks from websites.
The band's management, Ignition, said in a statement: "The MP3s of Oasis tracks in circulation appear to be illicit recordings (probably made with a hidden Walkman or similar device) of early mixes of the tracks for the band's new album, which were made some time ago.
"We hope anyone who has downloaded the tracks enjoys them but does not take them as any indication of the finished album which has come a long way since these recordings were made."
The statement added that the recordings were of a "poor quality".
Oasis released their first new material in two years, The Hindu Times, this week and the single is expected to top the charts on Sunday.
Earlier this month four tracks from the album appeared on the net - Songbird, Stop Crying Your Heart Out, She Is Love and Little By Little.
Sales slump
A spokesman for Sony said: "A lot of major artists preparing to release a new album find their music has been stolen and put out on to the Internet.
"There are some Oasis tracks out there on various sites and we will do what we always do in these circumstances, and that is close them down."
The music industry has seen sales slump by 5% worldwide as a result of mass copying and Internet piracy, according to figures released this week.
The International Federation of the Phonographic Industry said digital downloading was a serious problem.
Jupiter MMXI, a UK internet research company, is warning Europe's record companies that they must do more to stop music piracy.
Spokesman Mark Mulligan said the US is doing more to stop illegal downloading.
He said: "Europe's record industry needs to crack down hard and fast on the software companies behind file sharing networks.
"In the United States the record companies are starting to license content, but that's not happening in Europe."