An American professor, who took his son to New Zealand 18 months ago during a custody dispute, has been arrested on his return to the United States.

Police in the Oregon city of Beaverton say Marc Marenco, 59, had been arrested after flying into San Francisco and was held for extradition from California to Oregon.

The police say the 11-year-old boy and his biological mother, who has been granted sole custody, were reunited on Tuesday at the airport.

After he left the country, Dr Marenco was indicted in Washington County, Oregon, for "custodial interference".

A court in New Zealand also found in the mother's favour and ordered Dr Marenco and his son to return to the US.

Yale and Oxford-educated Dr Marenco, a philosophy professor at Oregon's Pacific University, created a website last June saying he was living in Dunedin with his son and teenage daughter.

He said a colleague had emailed him saying posters around Forest Grove, Oregon, claimed his son was missing and listed Marenco as his "abductor".

He denied abducting his son and claimed he was given "sole legal and physical custody" of both children in 2008 after a restraining order on their mother.

On his Linkedin site he wrote he was on sabbatical from Pacific University and was a research associate at Otago University's bioethics centre.