Kansas City Chiefs cornerback Marcus Peters raised his fist on Sunday during a performance of the U.S. national anthem, the latest gesture by a National Football League player to draw attention to racial inequality.

San Francisco 49ers backup quarterback Colin Kaepernick began the protests against injustice and police brutality when he refused to stand for "The Star-Spangled Banner" during preseason games, at first choosing to sit on the bench and then later kneeling on one knee in a gesture that has divided fans.

Other players have followed suit, including Denver Broncos linebacker Brandon Marshall before Thursday's season opening win against the Carolina Panthers.

The gesture on Sunday by the 23-year-old Peters, who is African-American, recalled the raised fist demonstration by black athletes Tommie Smith and John Carlos during their medal ceremony at the 1968 Olympic Games in Mexico City.

The rest of the Chiefs team stood with interlocked arms during the anthem before their season opener against the San Diego Chargers on Sunday, which is also the 15th anniversary of the Sept. 11, 2011, attacks.

Team members said they decided to lock arms as a sign of "solidarity" after discussing the issue as a group.

"It was our goal to be unified as a team and to be respectful of everyone's opinions, and the remembrance of 9/11," the team said in a statement. "It's our job as professional athletes to make a positive impact on our communities and to be proactive when change is needed."

The Seattle Seahawks also locked arms while standing during the national anthem before their season opener against the Miami Dolphins on Sunday.

It was not immediately clear with whom or to what cause the teams were showing solidarity, since Kaepernick's protest involved kneeling or sitting for the anthem. Representatives for the teams could not be immediately reached.

The protesting players have been praised as allies of the Black Lives Matter movement, which grew in response to a string of high-profile police killings of unarmed black people across the country. About two-thirds of NFL players are black.

The protests have also provoked anger in some fans who see the gesture as disrespecting the U.S. flag, the military, and the country in general.

To mark the 15th anniversary of the World Trade Center attacks, the league said it will play videotaped messages from President Barack Obama and his predecessor, George W. Bush, before each game, and a 9/11 decal will be placed on players' helmets.

The Seattle Seahawks have said they have decided as a team to stand and also lock arms during the anthem on Sunday.

"Progress can and will be made only if we stand together," Doug Baldwin, a Seahawks wide receiver, said in a video he posted online announcing the team's decision.

Kaepernick's 49ers play their opening game against the Los Angeles Rams on Monday evening. Obama has defended Kaepernick, saying this week the player is exercising a constitutional right and provoking conversation "around some topics that need to be talked about."

(Reporting by Jonathan Allen in New York and Curtis Skinner in San Francisco; Editing by Alan Crosby and Peter Cooney)