PORTLAND, Ore. – Thousands of labor and immigrant rights activists took to the streets Monday for a wave of protests in conjunction with May Day, a day that sparks protests annually among progressives but which took on a sharper edge this year over concerns about President Trump’s agenda.

While the protests were largely peaceful, a march in Portland, Ore., turned violent when a sea of black bloc anarchists set fire to newspaper boxes, slashed the tires of police vehicles and sprayed anarchy signs on storefronts. Police revoked the protest permit and declared the scene a riot, arresting at least nine demonstrators.

In New York, several protesters were arrested for blocking the entrance to Wells Fargo over the bank’s role financing private Immigration and Customs Enforcement detention centers, according to local news reports. In Oakland, Calif., four protesters were arrested for trespassing after sneaking past security at the Alameda County government building and unfurling a sign related to sanctuary cities, according to the sheriff’s office.

The protests focused primarily on immigration and labor. Groups urged immigrant workers to skip work, school and shopping to highlight their impact on the economy. In Austin, activists staged a sit-in at the governor’s office at the capitol complex to protest a Texas bill increasing immigration enforcement in Texas.

The demonstrations occurred as the scope of Trump’s approach to immigration is coming into focus. Immigration arrests rose 33 percent in the first weeks of the Trump administration, including thousands of people who were unlawfully present but otherwise had no criminal record, according to a Washington Post analysis. He has pledged to build a wall that stretches across the U.S.-Mexico border, despite a number of setbacks.

Meanwhile, tensions are rising between far-left and far-right activists. While masked, black-clad activists on the left have been known to vandalize storefronts and damage cars, they have mobilized heavily in the wake of Trump’s election to oppose his supporters, particularly those who espouse racist views.

Groups of Trump supporters, including members and allies of the loose coalition of far-right activists known as the alt-right, have recently become engaged in opposing the “antifa” groups – sometimes violently – and accuse them of trying to block free speech.

In Seattle, at least two people were arrested when a large anti-Trump contingent and a smaller pro-Trump group converged at Westlake Park. The event appeared peaceful otherwise in the early evening, and Mayor Ed Murray said it was the smallest May Day turnout he had seen during his four years in office, according to the Seattle Times.

But in Portland, where the May Day march included a large contingent of black bloc anarchists and “antifascists,” there was massive damage left in its wake. As the march turned by the federal courthouse in the early evening, rocks collided with the windows. Soon a smoke bomb went off, then Pepsi cans flew over the crowd at police.

After police announced that the permitted protest was now illegal, the antifa crowd ran south, smashing windows, lighting fires and spray-painting businesses.

By rush hour, Portland police had protesters detained by city hall, making at least nine arrests. Three fires were set in major intersections. Windows and ATMS were sprayed with red anarchy signs.

May Day has roots as a spring festival in European pagan cultures, but it was dubbed International Workers’ Day by socialist, anarchist and communist groups. The moniker commemorates the Haymarket affair, the name given to the violent confrontation that took place in Chicago in 1886 between police and union strikers demanding an eight-hour workday.

It became associated with immigrant workers in the United States in 2006, after weeks of massive protests over a bill that would have cracked down on immigrants in the country illegally. The marches, which took place in the spring and on May 1, are credited with energizing Latino workers and killing the bill, although demonstrators did not achieve their goal of comprehensive immigration reform.