Sara Jane Moore, who fired a handgun at US President Gerald Ford in an attempted assassination outside a San Francisco hotel in 1975, has died, according to US media.

Moore, who was sentenced to life in prison but was freed on parole in her final years, was 95.

Her attack came just days after Ford, a Republican, was targeted in an unrelated murder plot by associates of cult leader Charles Manson.

Ford was not injured in Moore's attack, which she said was intended to spark an American revolution. Her death comes amid renewed attention to presidential security following two attempts on President Donald Trump's life.

On 22 September, 1975, Moore fired a .38-caliber revolver she had purchased hours earlier at Ford, but missed.

A former US Marine standing nearby in the crowd of some 3,000 people then subdued her, forcing her to miss her second shot.

Moore had been arrested a day earlier after a security official spotted her with a gun at a gathering for Ford. That gun was confiscated, leading her to purchase another.

The mother-of-four from California pleaded guilty and was sentenced to life in prison. She served 32 years before she was released on parole.

Her attack occurred just 17 days after Manson follower Lynette 'Squeaky' Fromme pointed a gun at the president but failed to fire before she was apprehended.

Moore's death came just days after the 50th anniversary of her attempt.

In a 2009 interview with NBC News, Moore described how she had become radicalized by social upheaval in the 1960s and 1970s.

It was a time that people don't remember. You know we had a war... the Vietnam War, you became, I became immersed in it. We were saying the country needed to change, she told NBC. The only way it was going to change was a violent revolution. I genuinely thought that [shooting Ford] might trigger that new revolution in this country.

Investigators found no connections with revolutionary groups and judged her to be legally sane.

Just recently, Ryan Routh was found guilty of attempting to assassinate Trump on a Florida golf course last year. He will be sentenced on 18 December and faces up to life in prison.