LOS ANGELES, United States (AFP) - California announced new quarantine guidelines on Wednesday for people arriving in the western state deemed to pose a risk of spreading Ebola.

The new rules, announced by California's Department of Public Health (CDPH), mandate a 21-day quarantine for anyone travelling from Ebola-afflicted countries who has had contact with anyone stricken by the killer disease.

"Today we're establishing a statewide, standard protocol requiring some level of quarantine for those at highest risk of contracting and spreading Ebola," said CDPH director Ron Chapman.

"This order will protect the health and safety of Californians and support the state's local health officers' existing authority to develop protections against disease spread," he added.

Specifically, the order requires anyone who has "travelled to California from an Ebola affected area and has had contact with someone who has a confirmed case of Ebola... to be quarantined for 21 days.

"A person travelling to this region that has not come into contact with a person with Ebola will not be subject to quarantine," it said, adding that "affected areas" includes Guinea, Liberia and Sierra Leone, in West Africa.

Federal US health authorities on Monday issued new guidelines for health workers returning from Ebola-hit nations after a firestorm of criticism over state quarantine restrictions.

The enforced quarantine in New Jersey of a US nurse who had come home after treating patients in Sierra Leone sparked controversy - and accusations from the woman that her rights had been violated.

The nurse was discharged on Monday, one day after New York eased strict new quarantine rules under pressure from President Barack Obama's administration.

The US Centres for Disease Control and Prevention (CDC) on Monday urged "active monitoring" of those at risk following stints in the countries hardest hit by the epidemic - Guinea, Liberia and Sierra Leone.

"Active direct monitoring" means high-risk people must be checked for fever daily for 21 days, and must restrict their travel and public activities for the duration of the virus' incubation period, the CDC said, in an update of previous guidelines.

The Pentagon on Wednesday ordered a 21-day quarantine for all troops returning from West Africa, exposing a split between the US military and other government agencies, who favour less strict measures.