Three college football players from Michigan State University raised their fists during the US national anthem on Saturday, emulating NFL players who have chosen the gesture to protest racial inequality.

The protest by fullback Delton Williams, defensive end Gabe Sherrod and safety Kenney Lyke - who are all black - took place at the outset of Michigan State's home game against Wisconsin, rivals in the popular Big Ten conference, the Michigan news website reported with a photo of the three.

Sherrod had suggested in a Twitter message earlier in the week he would join in the protests that have grown in recent weeks among athletes in the United States to decry racial injustice and police brutality.

"Time to represent this movement publicly!! Our lives matter too and even us privileged college students fear for our lives around the police," Sherrod wrote.

The protest came during a fifth day of marches in Charlotte after a black man was shot and killed on Tuesday by a police officer in the North Carolina city, the latest flashpoint for a national wave of outrage over police violence against minority groups.

The protests during "The Star Spangled Banner" have spread since San Francisco 49ers quarterback Colin Kaepernick said he chose to stay seated during the national anthem before a National Football League pre-season game in August and then opted to kneel in the next game.

Players from several NFL teams have protested during the anthem since then, either by kneeling or raising their fists, while US women's soccer star Megan Rapinoe has also knelt during games.

The fist-raising protests recall the famous gesture by US athletes Tommie Smith and John Carlos during a medal ceremony at the 1968 Olympic Games in Mexico City.

The protesting players have been seen as allies of the Black Lives Matter movement, which grew in response to a string of high-profile police killings of unarmed African-Americans across the country in the last two years.

Other athletes and fans have spoken out against the protests, viewing them as disrespectful of the flag, the military and the nation in general.