US singer Madonna, who has promoted school building in the African country Malawi, is now turning her star power onto projects to improve the notorious slums of Rio de Janeiro.

The 51-year-old star is in Rio to visit some of the Brazilian city's slums, or "favelas", and meet with one of the country's richest businessmen to discuss setting up social projects, said state Governor Sergio Cabral.

"She will get to know some social projects; she is enchanted with Rio and wants to help," Cabral said. The beachside city has about 1,000 slums, many of them controlled by violent drug gangs or other armed groups.

A major outbreak of violence last month, which followed Rio's selection to host the 2016 Olympics, underlined its stubborn security and poverty problems.

Madonna last month launched the construction of a multimillion dollar girls' school she is funding in Malawi, from where she has adopted two children.

The divorced singer has been linked romantically in media reports to a 23-year-old Brazilian model Jesus Luz.