Governor Gavin Newsom on Monday admonished Californians who flocked to beaches by the thousands at the weekend, warning that their behavior could reverse progress made in combating the coronavirus pandemic.

"We can't see images like we saw, particularly on Saturday, in Newport Beach and elsewhere," Newsom told reporters, referring to photos showing people packing several beaches in southern California amid a heatwave.

"The virus doesn't take the weekend off because it's a beautiful sunny day around our coasts," he added.

The images from Newport Beach and neighboring Huntington Beach have prompted a backlash, with many comparing them to photos in April of beachgoers in Florida that sparked the #FloridaMorons hashtag.

Newsom said that while the most populous state in the country is weeks away from starting to gradually lift stay-at-home orders, the beach scenes from the weekend could push back that goal.

"The only thing that will set us back is our behavior," he said.

"The only thing that can stop that is more images like we saw this weekend."

Beaches in California have been closed to the public because of the pandemic, but a handful of cities have moved to allow visitors while enforcing restrictions, including for parking and social distancing.

California was the first state in the nation to impose a stay-at-home order in early March, a move largely seen as having contributed to preventing a death toll similar to those in New York or New Jersey.

The western state has registered nearly 45,000 cases of COVID-19 so far with almost 1,800 deaths, a fatality rate deemed modest considering the size of the state.

Newsom said he plans to work with local officials to reassess enforcement measures to avoid a repeat of the weekend beach scenes.

The city council in Newport Beach said on Monday it was considering closing the beaches for the next three weeks or blocking roads to avoid large crowds.

- Life goes on -

Los Angeles County's public beaches, which include Santa Monica, Venice and Malibu beaches, for their part are closed to the public until May 14, as are public hiking trails, bike paths and piers.

"We won't let one weekend undo a month of progress," Los Angeles Mayor Eric Garcetti tweeted Sunday. "While the sunshine is tempting, we're staying home to save lives."

On Monday, several beaches in San Diego and nearby towns opened for recreational activities such as walking or swimming, but group gatherings and sunbathing were not allowed.

In Huntington Beach, located about 40 miles (65 kilometers) south of Los Angeles, law enforcement officials said that while the weekend photos of beachgoers seemed impressive, most people kept their distance from each other.

"Despite what's being reported, the majority of our beach goers are complying (sic) to social distancing,"  Huntington Beach police tweeted.

In a statement, the city said police and lifeguards patrolling the beach found "the majority of people staying in their own unit."

Lifeguards also used loudspeakers to issue social distancing reminders every hour.

"This is the first time I've been out since March 23, so I'm doing my due diligence," Amy Hughes, one of the beachgoers, told AFP on Saturday. "We are keeping our distance, and life still has to go on."

Andrew Matthew, another beachgoer, also insisted that people were respecting social distancing guidelines and needed to get a break from weeks of hunkering down at home.

"We're in open space, keeping six feet apart," he said. "And it's getting hotter and hotter."