Demonstrations protesting the U.S. presidential election victory of Republican Donald Trump entered their second week on Monday, with thousands of students chanting phrases like "Not My President" after walking out of classes across the country.

The latest protests came as critics slammed Trump's selection of right-wing firebrand Stephen Bannon as his chief strategist, with many fearing the move could lift the white nationalist movement into the top levels of the White House.

The Los Angeles Unified School District estimated that 4,000 students walked out of classes across the city in protest of the president-elect, who campaigned on deporting undocumented immigrants and building a wall between the United States and Mexico.

Officials with Seattle Public Schools said about 5,000 students walked out of 20 high schools and middle schools on Monday. That figure represented about 10 percent of the district's student body, according to schools spokesman Luke Duecy.

Authorities in Portland, Oregon, Montgomery County, Maryland, and the San Francisco Bay Area said hundreds of young people marched in protest as well.

Tens of thousands of people have marched in cities from New York to Los Angeles in largely peaceful rallies since Trump's upset victory last Tuesday over Democrat Hillary Clinton. Trump secured enough votes in the 538-member Electoral College to win the presidency despite trailing Clinton in the popular vote.

But there have been sporadic bouts of destruction. Demonstrators in Oakland, California, last week threw objects at police in riot gear and smashed storefront windows.

More than 100 people had been arrested following days of protest in Portland, Oregon, police said on Monday. Protesters in that city over the weekend blocked traffic and threw objects at police dressed in riot gear who responded with pepper spray and flash-bang devices.

Civil rights groups and police have monitored violence against U.S. minorities since Trump's win, citing reports of attacks on women in Islamic head scarves, of racist graffiti and of bullying of immigrant children.

Trump has called for peace and unity and denounced white supremacist groups that supported him. He said on Sunday he was "so saddened" to hear about racial slurs and personal threats made against African-Americans, Latinos and gay people by some of his supporters.

"I say, 'Stop it.' If it - if it helps," Trump told CBS' "60 Minutes" in an interview.

-Reuters