Female vocalist Utada Hikaru's track "Flavor of Life" could well be the world's all-time biggest-selling digital single, with sales of 7 million units across all digital products and formats, her label EMI Music Japan reports.

These include master ringtones, full-track mobile downloads, fixed-line downloads (including EMI's new premium DRM-free downloads), ring videos and ringback tones, plus two different mixes of the song.

The physical single has sold some 700,000 units, adds the label.

According to local labels body the Recording Industry Assn. of Japan (RIAJ), the market's previous best-selling digital single was 2005's "Dragostea Din Tei" by Moldavian pop act O-zone, which sold some 4 million units, mainly comprising master ringtones.

The top-selling digital track in the U.S. to-date, according to Nielsen SoundScan, is Daniel Powter's "Bad Day," which sold just over two million units in 2006. That figure excludes master ringtones.

According to Nielsen RingScan, the best-selling master ringtone of all time the United States is the 2.1 million-selling "Smack That" by Akon.

"Utada Hikaru has once again led the Japanese music market into new areas of growth and success," said EMI Music International chairman/CEO J.F. Cecillon in a statement.

"Flavor Of Life" has firmly established a new form of hit single - one where consumers can purchase music in whatever ways they choose. In the new music environment, we must deliver multiple products for multiple consumers."

"Flavor of Life" was used as the theme song for TV drama series "Hana Yori Dango," (meaning Boys Over Flowers), which broadcast on the TBS network.

The ballad version of "Flavor Of Life" was first released as a master ringtone on Jan. 5 to tie in with the launch of the series, which featured the song in its entirety at the end of almost every episode.

Additional digital product types, such as ringvideos, ringback tones and master ringtones of the original version of the song were released in the following weeks.