Six US mayors called on Congress to stop Trump from sending federal forces to cities due to concerns about escalating tensions with protesters.

Numerous US federal agents have been recently deployed by the administration of President Donald Trump to Portland, Oregon to stop anti-racist protests.

"We urge Congress to pass laws to make it clear that these actions are illegal and unacceptable," the mayors of six cities, including Portland, Chicago, Seattle, Albuquerque, Kansas and Washington, DC.

Trump said national unrest, including the destruction of protesters' historic statues, was the reason he deployed federal forces to cities.

The Department of Homeland Security, meanwhile, said its agents in Portland and other cities were only aiming to protect federal assets from "anarchist violence."

Anti-racist protests in the US continued to intensify over the weekend, after a person was shot dead in Austin, Texas on July 25.

In Seattle, police arrested 45 people during a protest protesting the presence of federal agents.

Protesters in Oakland, California, set fire to a court, broke police stations, banged windows, painted graffiti, fired fireworks and shone lasers at police after peaceful protests on the evening of July 25 disappeared.

A wave of anti-racist protests and police violence broke out in the US in late May, after black man George Floyd was murdered by police in Minneapolis.