Elizabeth Smart's kidnapper, Wanda Barzee, was back behind bars for a brief moment ... because she was arrested in Utah for allegedly violating the conditions of her supervised release.

Police in Salt Lake City tell TMZ ... Wanda was arrested Thursday after detectives discovered she allegedly visited at least two public parks in town.

The issue ... Barzee is a registered sex offender in Utah and going to a public park is a big no-no for her.

Cops say Barzee allegedly went to Liberty Park and Sugar House Park ... and she was booked into Salt Lake County Metro Jail on one count of violating Utah's law restricting registered sex offenders from entering protected areas, including public parks.

As you know ... Barzee pled guilty to helping kidnap 14-year-old Smart in 2002, and Smart says Wanda stood idly by as her other abductor, Brian David Mitchell, repeatedly raped her.

Barzee was released from Utah state prison in September 2019 after 15 years behind bars. Meanwhile, Mitchell is serving a life sentence in Arizona.