Oprah Winfrey, stars of Selma march in Alabama in honour of Martin Luther King, Jr.

Actors from the movie Selma marched with hundreds of people Sunday to recall one of the bloodiest chapters of the civil rights movement, while America prepared to mark the national holiday honouring Martin Luther King Jr.

The remembrance comes after several incidents around the country in which unarmed black men were killed by police in recent months, leading to protests. In Ferguson, Mo., the site of the most persistent protests, leading black members of Congress pressed for further reforms of the criminal justice system in the name of equality.

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Eight members of the Congressional Black Caucus joined U.S. Representative William Lacy Clay in Ferguson as they took up King's legacy in light of the recent deaths.

"We need to be outraged when local law enforcement and the justice system repeatedly allow young, unarmed black men to encounter police and then wind up dead with no consequences," said Clay. "Not just in Ferguson, but over and over again across this country."

In Selma, Ala., Oprah Winfrey helped lead the march with Selma director Ava DuVernay, actor David Oyelowo, who portrayed King in the movie, and the rapper Common. They and others marched from Selma City Hall to Edmund Pettus Bridge, where civil rights protesters were beaten and tear-gassed by officers in 1965.

"Every single person who was on that bridge is a hero," Winfrey told the marchers.

The film chronicles the campaign leading up to the historic march from Selma to Montgomery, Ala., and the subsequent passage of the 1965 Voting Rights Act.

Law enforcement officers used clubs and tear gas on March 7, 1965 — "Bloody Sunday" — on marchers intent on seeking the right for blacks to register to vote. A new march, led by King, began two weeks later and arrived in Montgomery days later with the crowd swelling to 25,000.

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McLinda Gilchrist, 63, said the movie should help a younger generation understand what life was like in the 1960s during the struggle to end racial discrimination. "They treated us worse than animals," Gilchrist said.

MLK Day observed across U.S.

For Monday's federal holiday, people around the country were remembering King's leadership, some in light of the fatal police shootings that had recently shaken the U.S., including the death of an unarmed black teen last year in Ferguson, Mo.

Eight members of the Congressional Black Caucus joined U.S. Representative William Lacy Clay in Ferguson on Sunday as they invoked King's legacy. They vowed to seek criminal justice reform.

"We need to be outraged when local law enforcement and the justice system repeatedly allow young, unarmed black men to encounter police and then wind up dead with no consequences," the Democrat said. "Not just in Ferguson, but over and over again across this country."

The life and legacy of the Rev. Martin Luther King Jr. also was being celebrated at the church he pastored in Atlanta.

MTV goes black and white

In honour of Martin Luther King Jr. Day, all of the U.S. network's programming is airing in black and white.

The network is featuring interviews with celebrities and public figures discussing their own experiences and reflections on race.

The move is part of the channel's "Look Different" campaign that launched in April 2014 in an effort to get young people engaged in discussions about race, gender and sexual orientation. 

The campaign created commercials with civil rights groups including the NAACP in the aftermath of the fatal police shooting of 18-year-old Michael Brown in Ferguson, Mo., last summer. The network also aired a special, Laverne Cox Presents: The T Word, about transgender youth with the Orange is the New Black star.