A documentary film-maker whose work rescuing children from squalid Romanian orphanages in the early 1990s inspired Virgin tycoon Sir Richard Branson, has been shot dead after a dispute with a neighbour over foliage.

The San Diego County Sheriff's Department said Michael Vilkin, 61, had been arrested on suspicion of the murder of John Upton, 56, of Encinitas, California.

The department said a dispute between the two men led to the shooting.

After learning of the plight of Romanian orphans in 1990, Mr Upton publicised the brutal conditions and was instrumental in bringing around two dozen orphans to America for medical care and adoption.

His work in Romania also gained the attention of influential activists, inspiring Sir Richard and actress Jessica Lange to help rescue youngsters from Romania.

Mr Upton went on to create an online network of films about charitable causes.

Vilkin, in an interview conducted in county jail, told KGTV in San Diego he fired in self-defence after Mr Upton menaced him with a gun.

He said he owned vacant property next to Mr Upton's home and the two men had a disagreement over trimming shrubs.

"I did not go to him," he told the station. "He came to me threatening and pulled a gun (on) me."

Mr Upton's brother Michael told U-T San Diego that his brother and Vilkin argued previously about trees.