San Francisco 49ers quarterback Colin Kaepernick was subjected to loud booing on Thursday after once again refusing to stand during a rendition of the US national anthem.
Kaepernick has triggered furious debate in the United States over his decision to sit during the playing of 'The Star Spangled Banner' in a protest aimed at drawing attention to the plight of black Americans.
The 28-year-old signal-caller crouched on one knee during the anthem on Thursday as the 49ers prepared to face the San Diego Chargers at the Qualcomm Stadium in Southern California.
His latest protest -- which drew support from team-mate Eric Reid, who also knelt - came on a night when the Chargers honoured US military personnel in a 'Salute to the Military'.
As Kaepernick knelt near the 49ers bench, a navy officer sang the anthem while 240 sailors, Marines and soldiers presented a US flag and emblems from branches of service.
Following the rendition of the anthem, the crowd booed Kaepernick relentlessly every time he took a snap.
A banner in the crowd read: "You're an American. Act like one."
However, the jeering did little to deter Kaepernick, who led the team on a smooth 16-play opening drive for an early touchdown to put the 49ers ahead.
His protest has divided opinion, with many decrying his actions as disrespectful or unpatriotic.
Republican presidential nominee Donald Trump described Kaepernick's anthem boycott as a "terrible thing," suggesting the player should move to another country.
"Maybe he should find a country that works better for him, let him try, it's not going to happen," Trump said.
However, Kaepernick's stance has won applause from veteran civil rights campaigners and sporting icons including Tommie Smith, the sprinter who was ostracized for his clenched fist salute alongside John Carlos at the 1968 Mexico City Olympic Games.
"He's being vilified in how he brings the truth out," Smith said on Tuesday. "I support him because he's bringing the truth out - regardless of how done. If it's not done violently, at least he should be heard."
Speaking before the kick-off, Chargers fullback Chris Swain - a Naval Academy graduate - said he respected Kaepernick's right to protest the anthem.
"I stand and show respect for it, but he has the right to do what he wishes and I respect that," he told 10News local television.