US President Donald Trump has urged supporters to "liberate" three states led by Democratic governors, apparently encouraging the growing protests against stay-at-home restrictions aimed at stopping the coronavirus.

Key points: Many Americans in regions that have not seen major outbreaks have urged governors to reopen their states

Many Americans in regions that have not seen major outbreaks have urged governors to reopen their states Protestors have gathered outside state government buildings across the country

Protestors have gathered outside state government buildings across the country Governors of both parties have called for federal assistance with testing so businesses can reopen

A day after laying out a road map to gradually reopen the crippled US economy, Mr Trump took to Twitter with the kind of rhetoric some of his supporters have used in demanding the lifting of the orders that have thrown millions of Americans out of work.

"Liberate Minnesota! Liberate Michigan! Liberate Virginia, and save your great 2nd Amendment. It is under siege!" he said in a tweet storm in which he also lashed out at New York Governor Andrew Cuomo for criticising the federal response.

Mr Trump has repeatedly expressed his desire to see businesses reopen quickly and claimed earlier this week that he had total authority over the matter, even though the lockdowns and other social-distancing measures had been imposed by state and local leaders, not Washington.

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The shutdowns have inflicted heavy damage on economies around the world.

In the US, the crisis has cost at least 22 million Americans their jobs, pushing the unemployment rate toward levels not seen since the Great Depression.

In Florida, protesters have been calling for the relaxing of the state's coronavirus prevention measures. ( AP: John Raoux )

Many Americans, especially in rural areas and other parts of the country that have not seen major outbreaks, have urged governors to reopen their economies.

Protesters have taken to the streets in Ohio, Texas, North Carolina, Kentucky, Virginia and Michigan, where more than 3,000 turned out on Wednesday (local time), some wearing MAGA (Make America Great Again) hats and Trump flags.

The protests continued, including one outside the home of Governor Tim Walz of Minnesota and another in Idaho, where the governor is a Republican.

More than 1,000 protesters gathered at the Idaho Statehouse in defiance of Governor Brad Little's extension of the statewide stay-at-home order to the end of April.

Minnesota Governor Tim Walz says the state needs to improve its testing capacity before it can relax restrictions. ( AP: Glen Stubbe/ Star Tribune )

The extension was met with derision by some members of the far right in Idaho, and some libertarian, gun rights and anti-vaccine organisations began directing members to defy the order. Most at the Boise protest were standing shoulder-to-shoulder and not wearing face masks.

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Some carried signs claiming the coronavirus is a hoax, while others held signs with slogans like, "All workers are essential" and "Freedom not fear".

At least 400 people gathered outside the Governor's mansion in St Paul, Minnesota to demand relief after Mr Walz extended the state's stay-at-home order to May 4.

He has said the state needs to significantly expand its testing capacity before it can begin relaxing restrictions, even as he has come under increasing pressure from Republicans to move more quickly.

Dozens of cars circled Oregon's state Capitol to protest stay-at-home orders. ( AP: Andrew Selsky )

Many wore pro-Trump gear but very few practised social distancing or wore masks. Dozens carried American flags or signs bearing messages such as "Reopen MN". Others drove by in vehicles bearing signs denouncing the restrictions.

Mr Walz said he had tried calling the White House about Mr Trump's tweet but could not get through to the President or Vice-President Mike Pence.

In Oregon, dozens of people circled the state's Capitol in their vehicles to protest against the state's stay-at-home order.

Democratic Washington state Governor Jay Inslee said Mr Trump was encouraging "illegal and dangerous acts".

Public health experts have warned that an easing of the shutdowns must be accompanied by wider testing and tracing of infected people to keep the virus from coming back with a vengeance.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 32 seconds 1 m 32 s US President says he expects a COVID-19 death toll of up to 65,000

Governors of both parties have suggested they will be cautious in returning to normal, with some of them warning that they cannot do it without help from Washington to expand testing.

The official death toll in the US is near 35,000, with about 685,000 confirmed infections.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 20 minutes 20 m The Virus

AP