The US couple accused of kidnapping the 11-year-old Jaycee Lee Dugard and holding her for 18 years has denied all 28 charges.

Phillip Garrido, 58, and his spouse Nancy, 54, denied the charges during a brief court appearance on Friday.

Dugard, now 29, was abducted in 1991 while the girl was waiting for a school bus near her home in South Lake Tahoe, east of the city of San Francisco, by two people in a grey sedan.

Dugard was reunited with her mother and half-sister at a motel outside San Francisco on Friday.

According to police on Thursday, Dugard had been kept in a hidden backyard behind her captor's home and has had two children - aged 11 and 15 - with him during her years in captivity.

The police detained Garrido, a registered sex offender in California who had previously been jailed for rape and kidnapping, and his wife Nancy, on Wednesday.

"None of the children had ever been to school, none had been to a doctor, they were kept in complete isolation in this compound, if you will, at the house," Fred Kollar, the El Dorado County Undersheriff, told the Reuters news agency.

HRF/DT