President Donald Trump on Monday called the stabbing murders of two men on a metro train in Portland, Oregon, last week by a man who was shouting insults at two women he took for Muslims "unacceptable."

Until Monday, Trump had not yet made any statement about the killings last Friday, sparking criticism that he did not care about the attack, although the incident occurred while he was outside the country on his first trip abroad as president visiting the Middle East and Europe and coinciding with the start of Ramadan, the holy month in Islam.

"The violent attacks in Portland on Friday are unacceptable. The victims were standing up to hate and intolerance. Our prayers are w/ them," Trump said on Twitter.

Authorities arrested a suspect, Jeremy Joseph Christian, 35, and he is now facing two counts of murder and one count of attempted murder, as well as counts of intimidation and criminal possession of a weapon, Portland police said in a statement.

In addition to killing the two men who tried to intervene in his rant against the women he apparently thought were Muslims, the suspect stabbed and injured a third passenger who also tried to help.

According to police, what Christian was shouting at the women "would best be characterized as hate speech toward a variety of ethnicities and religions."