The mother-in-law of Formula One chief Bernie Ecclestone has been kidnapped in Sao Paulo and criminals are demanding 120 million reais ($36.5 million) in ransom, according to reports in a leading Brazilian news magazine.

Aparecida Schunck, the mother of Ecclestone's wife, Fabiana Flosi, was seized on Friday night, Veja and other news organizations reported.

It did not give more details, and local police could not be reached to confirm the reports.

Ecclestone, whom Forbes magazine estimates is worth $3.1 billion - along with his family - and one of the most powerful men in sport, married Flosi in 2012, three years after meeting her at the Brazilian Grand Prix.

Ecclestone, who is now 85, divorced his then wife of 25 years, Croatian model Slavica Radic, in order to marry the young Brazilian. The couple now live in England.

Kidnapping was common in Brazil a decade ago with several people seized each day, often for sums of just a few hundred dollars.

A crackdown by police, including the formation of a special anti-kidnap division, reduced the number considerably, and the crime has become much rarer.

Brazil is currently in the midst of its worst economic crisis in almost a century.