WASHINGTON — Texas Sen. Ted Cruz has called for a federal criminal investigation of an Oregon mayor, alleging that he allowed a conservative journalist to be assaulted by an anti-fascist group during a weekend protest.

"To federal law enforcement: investigate & bring legal action against a Mayor who has, for political reasons, ordered his police officers to let citizens be attacked by domestic terrorists," Cruz wrote on Twitter Sunday.

Portland Mayor Ted Wheeler, a Democrat who is also the police commissioner of the city, has not publicly responded to Cruz.

On Saturday, Antifa protesters assaulted and threw milkshakes at Andy Ngo, an editor for the conservative publication Quillette, at a Portland rally. Ngo frequently writes about the left-wing group, and in his Twitter bio he claims that he is "hated by the antifa." He later retweeted a video of him being attacked.

Multiple demonstrations by anti-fascist and right-leaning groups took place in downtown Portland on Saturday. The demonstrations turned violent when people started using pepper spray and throwing milkshakes that contained quick-drying cement, according to Portland police. Several officers were also reportedly assaulted, and three demonstrators were arrested.

In a two-minute clip Ngo posted on Twitter, he appears to be approached by an officer who is a medic. "I just got beat up by the crowd, no police at all, in the middle of the street, and they stole my GoPro," he said in the video. "They punched me several times in my face and my head."

Harmeet Dhillon, a lawyer and spokeswoman for Ngo, and a Republican national committeewoman from California, told the Daily Caller, a conservative publication, that Ngo was admitted to the hospital overnight for a brain bleed.

Ngo wrote on Twitter that he was admitted to the ER after being hit in the head. Dhillon blamed Wheeler's "total capitulation" to criminals and asserted that he had told his police to stand down.

Cruz responded to the attack with a barrage of Tweets calling on "mainstream journalists" to acknowledge the "sickening attack" and for law enforcement to "find & prosecute these violent felons."

CNN journalist Jake Tapper tweeted that Antifa frequently assaults journalists, calling it "reprehensible."

Rep. Kevin McCarthy, R-Calif., the House minority leader, condemned Antifa for a “cowardly attack.”

Others have also expressed outrage.

“It is not acceptable to assault journalists, no matter how much you hate their work. Trying to create carve-outs on this is a very bad idea that is unlikely to end well,” tweeted Matthew Gertz, a senior fellow at Media Matters for America.