Mayor Femke Halsema, of the Green Left party, said city authorities were caught off guard by the huge turnout, which was originally expected to be 200-300 people, and could not have intervened peacefully. She defended the public's right to demonstrate.

The Netherlands has recorded nearly 6,000 deaths from Covid-19. Authorities have issued fines of about £300 for violating rules not to hold public gatherings, but there were almost no police at Monday's event.

The demonstration, the largest in the Netherlands since lockdown measures were imposed in mid-March, sparked debate about whether the event could cause new infections.

"This is exactly what we don't want," Menno de Jong, a virologist at Amsterdam's UMC hospital and a member of the Dutch national coronavirus crisis team, told the Parool newspaper. "There is a reason we have been talking about social distancing for months. This could potentially be a so-called super spreading event."

Klaas Dijkhof, a member of parliament for the VVD party of Dutch prime minister Mark Rutte, said on Twitter he was "not only angry, but worried by the images out of Amsterdam". He called on demonstrators to voluntarily isolate themselves for two weeks.

Reuters