The US vice president, Mike Pence, has left an American football game after some of the players dropped to one knee during the national anthem.

The former Indiana governor flew in for the Indianapolis Colts-San Francisco 49ers game on Sunday but he did not stay long.

Around a dozen San Francisco players dropped to one knee during the national anthem, in protest over the oppression of blacks and other minorities.

The White House issued a statement from Mr Pence, in which he said Americans should rally around the flag.

Mr Pence is a noted sports fan and it is the second major event he has attended in his home state since taking office in January, after May’s Indianapolis 500.

He had wanted to honour Peyton Manning, who became the first Indianapolis-era player in Colts history to have his jersey number retired.

Meanwhile a US reporter has clarified his televised report saying that the player who began the kneeling protest had told him that he would stand during the national anthem if he returned to the NFL.

CBS reporter Jason La Canfora said he did not discuss the issue with quarterback Colin Kaepernick when they spoke on Saturday night.

He had earlier said during a TV interview: “He’s not planning on kneeling. He’s going to donate all his jersey sales and he’s planning on standing for the anthem if given the opportunity.”

But he tweeted later that he does not know what Kaepernick would do during the anthem.

Kaepernick kneeled during the national anthem last season to bring more attention to the killings of black men by police officers and other social injustices.

The protests spread this season after the former 49ers starter opted out of his contract and was unable to sign on with another team.

The issue has grown as Seattle Seahawks player Michael Bennett recently said he was racially profiled by Las Vegas police during a confrontation, and Mr Trump aggressively chastised players and team owners for protests during the anthem.