Only one Pittsburgh Steelers player could be seen as the American national anthem played ahead of their match against the Chicago Bears.

Alejandro Villanueva, who served in the army, stood at the entrance to the tunnel during the Star Spangled Banner while the rest of his team stayed in the dressing rooms.

The Steelers' protest is the most extreme yet as the protest movement against racial injustice in the US builds.

Some New England Patriots players took a knee during their anthem while others chose to stand and lock arms.

A total of 27 players knelt before the NFL game between the Jacksonville Jaguars and the Baltimore Ravens at Wembley this afternoon.

(Image: USA Today Sports)

(Image: Getty Images North America)

Ahead of the clash, US President Donald Trump had referred to players who chose to protest the anthem as "sons of b******" and insisted they should be fired.

He even suggested that fans should boycott the sport, during one of his trademark Twitter tirades.

Show Player

Both the Tennessee Titans and the Seattle Seahawks announced before their match in Nashville that they would both stay in the changing rooms during the anthem.

The home team made it clear that they weren't standing for or against protests, but rather together as a unit.

A statement from the Titans read: "As a team, we wanted to be unified in our actions today. The players jointly decided this was the best course of action.

"Our commitment to the military and our community is resolute and the absence of our team for the national anthem shouldn't be misconstrued as unpatriotic."

The Steelers said they "would not stand for the injustice that has plagued people of colour in this country."

"Out of love for our country and in honour of the sacrifices made on our behalf, we unite to oppose those that would deny our most basic freedoms.

"We remain committed in continuing to work towards equality and justice for all."

Fox TV didn't show the anthem, instead waiting for players to come onto the pitch but videos on Twitter showed the singer of the anthem take a knee during her performance.

(Image: Getty Images North America)

(Image: Getty Images North America)

(Image: USA Today Sports)

Before the Steelers kicked off, head coach Mike Tomlin told CBS: "These are very divisive times for our country and for us as a football team it is about us remaining solid. We’re not going to be divided by anything said by anyone.

"That's the thing I posted to our guys, I said if you feel the need to do anything I’m going to be supportive of that, as Americans that's our right. Whatever we do we're going to do 100 per cent, we're going to do together.

(Image: Getty Images North America)

(Image: @NFLonCBS/Twitter)

"We're not going to let divisive times or divisive individuals affect our agenda. This collection of men are chasing something in2017 and we're not going to play politics; we are football players and football coaches.

"We’re not going to participate in the anthem today, not to be disrespectful but to remove ourselves from the circumstance.

"People shouldn't have to choose; if a guy wants to go about his normal business and participate in the anthem he shouldn't be forced to choose sides. If a guy feels the need to do something, he shouldn't be separated from his teammate who decides not to.

"We’re not participating today, that's out decision, we’re going to be 100 per cent. We came here to play a football game and thats out intention. we’re going to play and play to win. We will not be on the field [for the anthem]."

(Image: Action Images via Reuters)

(Image: Action Images via Reuters)

(Image: Getty Images Europe)

(Image: PA)

Trump began his attacks on professional sports on Friday, when he told a rally: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say: 'Get that son of a b****** off the field right now, out. He's fired. He's fired!'"

In response, NFL Commissioner Roger Goodell called Trump's remarks "divisive."

He said: "The NFL and our players are at our best when we help create a sense of unity in our country and our culture.

"There is no better example than the amazing response from our clubs and players to the terrible natural disasters we've experienced over the last month.

"Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game, and all of our players, and a failure to understand the overwhelming force for good our clubs and players represent in our communities."

Further protests are expected back in the States before this evening's games.