An alleged extremist accused of stabbing two men to death when they challenged him over an anti-Muslim rant on the first day of Ramadan yelled "death to the enemies of America" when he appeared in court.

Jeremy Joseph Christian, 35, launched the attack after passengers objected to him screaming abuse at two young Muslim women travelling on a train in Portland on 2 May, it is claimed.

Prosecutors claim Christian fatally stabbed Ricky Best, 53, and Taliesin Meche, 23, when the pair tried to protect the girls, who have not been named.

Micah David-Cole Fletcher, 21, was also wounded during the knife attack and remains in a serious condition in hospital.

The suspect has remained defiant after being arrested and charged with aggravated murder, attempted murder, intimidation and being a felon in possession of a weapon.

When he appeared in Multnomah County Circuit Court on Tuesday he yelled: "Leave this country if you hate our freedom - death to antifa [anti-fascism].

“Free speech or die, Portland. You got no safe place. This is America - get out if you don't like free speech.”

About a dozen protesters in the hall outside the courtroom erupted into shouting while the charges were read.

Portland: Witness describes scene of triple stabbing on train

Mr Fletcher sat in the front row of the gallery during the arraignment, with a long, sutured wound visible on his neck.

If found guilty of the murder charges, Christian could face either life imprisonment or the death penalty.

Friday's stabbing attack came as some religious rights groups warn of a rising tide of anti-Islamic sentiment in the United States, blaming President Donald Trump for divisive anti-Muslim rhetoric.

One of the two women who was the target of the religious slurs on Friday, Destinee Mangum, who was with a friend wearing a Muslim head scarf, said in a video posted on CNN's website on Monday that she did not know the men who intervened and thanked them for putting their lives on the line.

Trump condemned the stabbings on Monday, calling them “unacceptable.” “The victims were standing up to hate and intolerance. Our prayers are w/ them,” he said on Twitter.

Trump's remarks came after the Council on American-Islamic Relations (CAIR) called on him to condemn the rampage and speak out against what the advocacy group sees as an increase in anti-Islamic sentiment. Anti-Muslim incidents increased more than 50 percent in the United States last year, it said.

Target of Portland killer’s hate speech thanks heroes who gave their lives

Asha Deliverance, the mother of Taliesin Myrddin Namkai-Meche, one of the two men who was killed on Friday, in an open letter to Trump that was posted on social media on Tuesday, urged the president to condemn âacts of violence, which result directly from hate speech.

According to The Oregonian, a witness to the stabbings said Namkai-Mecheâs last words before being taken away by paramedics were, "Tell everyone on this train I love them.“

On Monday, Portland Mayor Ted Wheeler called on federal authorities to rescind a permit for a 4 June “Trump Free Speech Rally” and not to issue a permit for a 10 June. “March Against Sharia.” In a Facebook post, he said, “Our community's anger is real, and the timing and subject of these events can only exacerbate an already difficult situation.”

The Oregon chapter of the American Civil Liberties Union replied with a statement on Twitter warning against censoring “unpopular speech.”

The Federal Bureau of Investigation is investigating the attack to determine whether to charge Christian with terrorism or a federal hate crime, Portland FBI spokeswoman Beth Anne Steele said.