ACT for America is spearheading National March Against Sharia rallies in at least 28 cities across the country.

Right-wing marchers have taken to the streets in several cities across the United States for the National March Against Sharia, an anti-Muslim campaign that has been roundly criticised by rights groups and watchdogs.

Responding to a call by ACT for America, march participants came out in at least 28 cities in some 20 states on Saturday.

The Southern Poverty Law Center (SPLC) has described ACT for America as an “extremist” organisation and the largest grassroots anti-Muslim group in the country.

Counterprotesters amassed in several cities to oppose the nationwide marches, with clashes and skirmishes taking place at a handful of the march sites.

Speaking to Al Jazeera before the marches, Corey Saylor of the Council on American-Islamic Relations (CAIR) described the marches as “Islamophobic” and part of a phenomenon that leads to the “creation of an environment in which violence [against Muslims] feels permissible”.

Alia Salem, a Dallas-based Muslim-American and social justice activist, argued that anti-Muslim xenophobia long predates the presidency of Donald Trump.

“Islamophobia wasn’t created by Donald Trump,” Salem told Al Jazeera.

“It was empowered to a certain extent. More than anything, the idea of white supremacy within segments of our population have been empowered through his presidency.”

READ MORE: How US groups spread hate via the Islamophobia industry

ACT for America did not reply to Al Jazeera’s request for a comment. A statement on the group’s website claimed that sharia – or Islamic law – runs contrary to human rights and the US Constitution.

Clashes reportedly broke out between anti-fascists – known colloquially as Antifa – and march participants in a handful of cities, including Seattle, Washington.

Freelance journalist Mike Bivins, reporting from Seattle, published on Twitter videos of a brawl between the two sides and police subsequently firing pepper spray into the crowds

ANTIFA JUST BEATDOWN A TRUMP SUPPORTER. HUGE WILD BRAWL. BATTLE IN SEATTLE!!!! pic.twitter.com/X4NHVlSeJe — Mikeford “Le Morte d'Michael” Biziths (@itsmikebivins) June 10, 2017

During a rally and counterprotest in New York City, local media reports estimate that around 200 Antifa protests outnumbered several dozen participants of the National March Against Sharia.

Images posted on social media showed skirmishes between the left-wing counterprotesters and the far-rightists, who had their “Make America Great Again” hats ripped off during confrontations.

Discriminatory history

Founded in 2007 and boasting of more than 500,000 members, the group is one of many that support US President Donald Trump. Its members have campaigned for strict legislation that targets Muslims and refugees in recent years.

In an executive order that has been frozen by courts, Trump has attempted to ban travellers from six Muslim-majority countries from entering the US. The order is slated to be considered by the Supreme Court.

In a report published last year, CAIR examined what it calls the “Islamophobia industry”.

Between 2008 and 2013, the report found, ACT for America was one of 33 anti-Muslim groups that had access to more than $204m in revenue.

Brigitte Gabriel, ACT for America’s founder, is a Lebanese American who has in the past accused the Muslim Brotherhood political movement of conspiring to conquer the US. She has also referred to Arabs as “barbarians” and claimed they have “no soul”.

Nathan Lean, author of The Islamophobia Industry, described ACT for America as part of “a network of bigots” that has promoted anti-Muslim sentiment in recent years.

“That sense of fear has not only led to the adoption of legislation that discriminates against Muslims, but has, in my opinion, spurred a smattering of hate crimes and other acts of violence and intimidation online and in the public that create a very dangerous situation for American Muslims,” he told Al Jazeera.

Between 2013 and 2015, at least 10 anti-Muslim laws were enacted by state legislatures, according to CAIR.

An addition 81 bills or amendments targeting Muslims were introduced during the same time period.

Last year alone, CAIR documented 260 anti-Muslim hate crimes and 2,213 bias incidents aimed at Muslims.

Increasing clashes

Members of the alt-right – a loosely knit movement that includes white supremacists, neo-Nazis and other far-right groups – participated in many of Saturday’s marches.

The protests and counterprotests in more than a dozen cities come at a time of increased tensions and frequent physical confrontations between Antifa and far-right activists.

In New York City, the pro-Trump nationalist group The Proud Boys and the Oath Keepers militia movement took part in the local march and in favour of what they deem “free speech”.

In response, the Metropolitan Anarchists Coordinating Council (MACC) staged a noise demonstrations with hopes of drowning out anti-Muslim chants.

“They have no intention of encouraging free speech,” Marisa Holmes, a spokesperson for MACC, told Al Jazeera by telephone.

The marches come just weeks after Jeremy Christian, a 35-year-old white supremacist, allegedly stabbed to death Ricky Best, 53, and Taliesin Namkai-Meche, 23, when they tried to stop him from harassing a pair of girls, one of whom wore a headscarf, on a light rail in Portland, Oregon.

A third man, 21-year-old Micah Fletcher, intervened and was severely injured with a stab wound to his neck.

Counterprotesters hold signs and shout slogans during an anti-Sharia rally in Seattle, Washington, on June 10, 2017 [David Ryder/Reuters]

“They are encouraging violence against the most oppressed and marginalised groups in our society, and the threat is real,” Holmes added.

“As we’ve seen in Portland and elsewhere, people are being physically attacked – and there have been fatalities.”

In La Porte, Texas, the Houston Socialist Movement and other anti-fascist groups counterprotested the local ACT for America march on Saturday.

“We need collective political action to oppose the fascists and do whatever we can to deny them a platform when they come out to spread their filth,” David Michael Smith of the Houston Socialist Movement told Al Jazeera.

“We need to make very clear that most people in this society oppose them and do not want them around.”

Alluding to the recent killings in Portland, Alia Salem concluded: “The more people of conscience start waking up and realising what is happening – like the three men who stood up in Portland – the more it shows that this is an issue that doesn’t just affect Muslims. It affects all of us.”

Follow Patrick Strickland on Twitter: @P_Strickland_