WASHINGTON (AFP) - US officials in Missouri have condemned raucous crowds who packed a pool and bar at a popular holiday venue after video footage of the weekend partying spread on social media.

The party at Lake of the Ozarks attracted furious criticism from nearby St Louis county, where many people travelled to the lake over the Memorial Day holiday despite concerns over the coronavirus pandemic.

Officials said that anyone who ignored protective measures to prevent the spread of Covid-19 should self-quarantine for 14 days or until they test negative.

The United States has started to lift coronavirus lockdowns, and the images of hundreds of party-goers in congested swimming pools fuelled the fierce public debate over the strategy.

"This reckless behaviour endangers countless people and risks setting us back substantially from the progress we have made in slowing the spread of Covid-19," St Louis county executive Sam Page said in a statement on Monday.

"Large crowds at Lake of the Ozarks showed no efforts to follow social distancing," the statement added.

The US holiday weekend, marking the start of the summer season, saw mixed responses to the partial easing of many lockdowns, with beaches often busy and some people wearing masks.

President Donald Trump went golfing, while New York Governor Andrew Cuomo delivered his daily coronavirus briefing on Monday from a popular beach on the state's Long Island.

The US has been the hardest-hit country in the pandemic, recording 98,000 deaths so far.