By Dan Whitcomb

LOS ANGELES (Reuters) - Pop star Britney Spears on Wednesday was unexpectedly released from the Los Angeles hospital where she was held for a mental evaluation, prompting celebrity photographers to chase her across the city.

Spears, who was taken to UCLA Medical Center by ambulance and under police escort a week ago, left the facility quietly, according to the Los Angeles Times slipping out with a small security detail.

But the paparazzi picked up the Grammy-winning entertainer's trail after she made it home and went out again. Television showed at least a dozen photographers surrounding her black Mercedes.

Spears, 26, was pursued by the paparazzi to the Beverly Hills Hotel until police arrived to break up the throng and escort her inside.

It was not immediately clear why Spears, who had reportedly been ordered to spend two weeks under evaluation, was released. A hospital spokesman declined comment, citing patient confidentiality laws.

The move comes one day after court papers were made public containing accusations by the Grammy-winning pop star's mother, Lynne Spears, that her self-styled manager, Sam Lutfi, had drugged her in a bid to take control of her life.

Spears' father, Jamie Spears, and attorney Andrew Wallete have been granted temporary control of her assets, including her house, pending further legal proceedings.

A Los Angeles judge has appointed a psychiatrist to determine if Spears is capable of understanding the legal proceedings around her.

The same judge issued a restraining order against Lutfi and put on hold the bitter custody battle between the entertainer and her ex-husband, Kevin Federline.

Spears, a chart-topping singer and former child star, has seen her personal life descend into turmoil since she filed for divorce from Federline in 2006, while in recent months Lutfi has become an almost constant presence in her life.

The Louisiana native was hospitalized in early January for a mental evaluation after becoming badly agitated when Federline's representatives tried to retrieve their two children at her house.

She left the hospital after a brief period and returned home.

On Thursday last week, Spears went to UCLA Medical Center for this most recent round of psychiatric evaluation.

(Editing by Bob Tourtellotte and Xavier Briand)