Police have arrested more than 400 protesters outside the US Capitol from the organisation Democracy Spring, which is seeking to remove big money from politics and combat restrictive voter identification laws.

The mostly calm demonstration resulted in arrests for what the US Capitol Police called "unlawful demonstration activity" such as crowding and obstruction.

Organisers vowed to repeat the demonstration every day for a week.

The protest was held "to demand Congress take immediate action to end the corruption of big money in our politics and ensure free and fair elections", Democracy Spring said on its website.

The group lists actor Mark Ruffalo and academic Noam Chomsky and dozens of well known activist groups among its supporters.

"We believe this is the people's house, and Congress should be responsive to the people. We need to protect voting rights," said Peter Callahan, the group's communications coordinator.

Protesters hoisted a scarecrow-like effigy of a corporate lobbyist holding money bags and a sign reading, "Warning: Massive civil disobedience is next".

Police arrested those who sat on the stairs of the East Front of the Capitol, the seat of the Senate and the House of Representatives.

Democracy Spring traces its roots to the end of the Occupy Los Angeles movement.

"We see populism on the rise on both sides of the spectrum," Mr Callahan said.

"Americans are sick and tired of their politicians being bought and paid for."

The group's rise coincides with the presidential campaigns of Democrat Bernie Sanders and Republican Donald Trump, both of whom speak against the influence of campaign contributions on politicians.

Reuters