LOS ANGELES - California governor Gavin Newsom announced on Thursday a mandatory overnight stay-at-home order limiting non-essential work, movement and gatherings in most of the most populous US state to slow down the spread of COVID-19.

The order requires generally that non-essential work, movement and gatherings stop between 10 pm and 5 am local time in counties in the purple tier, where COVID-19 transmission rates are highest. The order will take effect at 10 pm on Nov 21 and remain in effect until 5 am on Dec 21, according to the office of the governor.

"The virus is spreading at a pace we haven't seen since the start of this pandemic and the next several days and weeks will be critical to stop the surge. We are sounding the alarm," said Governor Newsom in a news release.

"It is crucial that we act to decrease transmission and slow hospitalizations before the death count surges. We've done it before and we must do it again," he added.

The order is designed to reduce opportunities for disease transmission. Activities conducted during 10 pm to 5 am are often non-essential and more likely related to social activities and gatherings that have a higher likelihood of leading to reduced inhibition and reduced likelihood for adherence to safety measures like wearing a face covering and maintaining physical distance, the new release stated.

A total of 41 of 58 California counties, comprising over 94 percent of the state's population of around 40 million, are now in the purple tier.