A flare is lit as people protest against the attendance of the US president to the upcoming Davos World Economic Forum, on January 23, 2018, in central Zurich.

Flag-waving demonstrators carried anti-globalist and environmentalist placards such as, "No Trump, no coal, no gas, no fossil fuels" as they marched near Zurich's financial district. Some protesters also broke through a security cordon in Davos — where protests are strictly forbidden — to demonstrate against the WEF and the U.S. president.

Thousands of anti-capitalist activists marched through Swiss cities Tuesday evening to protest President Donald Trump 's scheduled visit to the World Economic Forum .

People rally as they protest against the attendance of the US president to the upcoming Davos World Economic Forum, on January 23, 2018, in central Zurich.

Trump is due arrive in Davos on Friday for a much-anticipated speech to attendees at the forum.

Police estimate that 2,000 protesters demonstrated in Zurich and hundreds marched in public squares in Geneva, Lausanne and Fribourg.

Security is conspicuous in Davos and it's meant to be, as the Swiss Alpine town hosts the annual meeting of global business and political leaders.