Police were called to a Los Angeles supermarket today after paparazzi swarmed new mum, Naomi Watts, as she shopped for groceries.

Fearing for Watts' and other shoppers' safety, two LAPD officers ordered more than 30 paparazzi to leave the Whole Foods organic supermarket and its car park in the upscale LA suburb of Brentwood.

After buying a trolley full of groceries, the Australian actress was forced to hide in the supermarket's outdoor garden section while a female friend drove a silver Audi station wagon close to an exit door.

Watts, 38, is hot property with the paparazzi since giving birth to son, Alexander Pete Schreiber, in Los Angeles on July 25.

Watts' partner, actor Liev Schreiber, and their son were not on today's shopping expedition.

"The paparazzi just came from everywhere," a Whole Foods employee, who asked not be named for fear of losing her job, said.

"It becomes a safety issue for customers, especially in the car park, which is busy enough without all those guys with cameras."

Watts has made few public appearances since giving birth, but Hollywood photo agency X17 is claiming the first picture of Watts and Alexander.

It was taken yesterday as a smiling Watts and son were sitting at a Brentwood cafe.

Today, Watts, wearing black shorts, a loose-fitting white top and no make-up, did not seem bothered by the paparazzi.

As she shopped inside with her friend, photographers with small digital cameras followed her through the store while others with long lenses and video cameras shot her from windows and doorways at the front of the supermarket.

After Watts paid her grocery bill, the LAPD officers and supermarket security cleared the car park.

The King Kong star hid in the garden section, put on a straw hat and sunglasses and waited for her car.

The Whole Foods store, nicknamed Whole Pay Cheque by locals because of its expensive organic food, is located near Watts' multi-million dollar Brentwood mansion.