WASHINGTON (AFP) - Former US president Donald Trump vented fury at protesters outside the White House in 2020, saying: "Can't you just shoot them? Just shoot them in the legs or something?" according to then Defence Secretary Mark Esper.

In a new book, excerpts of which were reported on Monday, Mr Esper recalled sitting in the Oval Office with "the President red faced and complaining loudly about the protests under way in Washington" over the police killing of a black man.

"Can't you just shoot them? Just shoot them in the legs or something?" Mr Trump is quoted as saying in a preview of the book seen by the Axios news website.

The protests, which were marked by violence as protesters clashed with security forces, were part of a nationwide wave of demonstrations in the wake of the May 2020 killing of Mr George Floyd by Minneapolis police.

US Park Police and National Guard troops deployed tear gas and flash bangs to clear the largely peaceful protesters.

Mr Esper's account appeared to confirm previous reports of Mr Trump arguing that the military should intervene to quell the spiralling civil unrest.

An earlier book by journalist Michael Bender quoted sources saying the chairman of the Joint Chiefs of Staff, General Mark Milley, argued with Mr Trump against using the military as the then President demanded a stronger response.

Mr Bender had quoted Mr Trump as saying "shoot them in the leg - or maybe the foot... but be hard on them!"

Mr Esper publicly stated at the time that he opposed invoking the Insurrection Act, a rarely used 200-year-old law which permits troops to be actively deployed within the United States.

His stance reportedly enraged Mr Trump, and he was sacked in November 2020.

Axios said Mr Esper's book had been vetted by the Pentagon and reviewed by generals and Cabinet members.