Thousands of people across the United States have protested against "stay-at-home" orders after President Donald Trump encouraged people to defy coronavirus lockdown imposed by state governors.

US President Donald Trump, who will seek re-election in the 2020 elections, has called for reopening of economic activities saying enough coronavirus testing has been done - a claim refuted by several governors belonging to both parties.

An estimated 2,500 people rallied at the Washington state capitol in Olympia to protest against Democratic Governor Jay Inslee's stay-at-home order, defying a ban on gatherings of 50 or more people.

In Denver, hundreds of people gathered at the state capitol to demand the end to Colorado's shutdown. As protesters clogged streets with cars, healthcare workers in scrubs and face masks stood at intersections in counterprotest.

Stay-at-home measures, which experts say are essential to slow the spread of the virus, have battered the US economy and more than 22 million Americans have filed for unemployment benefits in the past month.

Demonstrations to demand an end have previously erupted at a few spots in Texas, Wisconsin and the capitols of Ohio, Minnesota, Michigan and Virginia.

Trump has faced criticism for the handling of the pandemic, which has killed more than 40,000 people and infected nearly 750,000 in the US.