Spears reportedly spent a day in rehab before shaving her head

Spears checked into an unnamed facility at the request of her mother and other family members, the reports said.

"We ask that the media respect her privacy as well as those of her family and friends," People quoted her manager Larry Rudolph as saying.

Spears was spotted by fans without her hair after shaving it off in a Los Angeles hair salon on Friday.

She reportedly spent one day in a rehabilitation centre in the Caribbean last week.

Drastic cut

Since splitting with husband Kevin Federline last year, Spears has been making headlines with her partying lifestyle.

People's website quoted a statement by Spears' management, which said: "Britney Spears has voluntarily checked herself into an undisclosed rehab facility today."

Potential bidders can view Spears' hair on the salon's website

Spears had her drastic haircut at Esther's Hair Studio in Tarzana, west of Los Angeles, on Friday, but was later seen wearing a blonde wig.

The salon has set up a website to auction the hair for more than $1m (�512,500).

A spokeswoman for the website said they had already received a number of bids.

"We have received many offers and we are currently in the process of separating the real ones from the bogus ones," she told the BBC News website.

The website, which offers bidders an "opportunity of a lifetime", says a portion of the proceeds will be donated to various unnamed charities.