US gun advocates are expressing outrage over the coronavirus-related closures of gun retailers in Los Angeles County, with the leading gun rights organisation filing a lawsuit against the state of California.

"The circumstances posed by the novel coronavirus outbreak are noteworthy, but do not excuse unlawful government infringements upon freedom," the National Rifle Association said in a lawsuit filed against California and other officials.

The lawsuit comes after Los Angeles County Sheriff Alex Villanueva said he would enforce a closure on gun stores as a "non-essential" business.

The state has ordered residents to stay at home and the closure of businesses that do not meet essential needs in a bid to slow the coronavirus outbreak.

However, California Governor Gavin Newsom said the decision to close gun stores would be left to local authorities.

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The NRA contends that firearms and ammunition retailers "arguably provide the most essential business function possible by enabling Californians to lawfully defend themselves, their loved ones and their property".

The lawsuit comes as gun and ammo sales have surged as some panic-driven customers stockpile weapons, along with toilet paper and hand sanitiser.

Los Angeles Sheriff Villanueva has said buying a gun during the outbreak is a "bad idea" that could cause more injuries.

"Particularly, you have a lot of people now that are at home - normally, they're not. Cabin fever sets in, you've got a crowded environment, people at home - weapons are not a good mix," he said.

Ammo.com, an online gun retailer, has seen a nearly eight-fold increase in revenue over the past month, saying there has been a jump in sales around the country, led by conservative Texas.

Australians must stay at least 1.5 metres away from other people. Indoors, there must be a density of no more than one person per four square metres of floor space.

If you believe you may have contracted the virus, call your doctor (don’t visit) or contact the national Coronavirus Health Information Hotline on 1800 020 080.

If you are struggling to breathe or experiencing a medical emergency, call 000.

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