JOHANNESBURG (Reuters) - South African media and e-commerce firm Naspers Holdings will merge two of its Russian internet sites with rival Avito.ru in a deal worth at least $570 million, the Financial Times reported on Tuesday.

Cape Town-based Naspers, which has transformed itself into a $29 billion internet powerhouse by buying business in fast-growing markets, plans to merge its Slando.ru and OLX.ru classified sites with Avito, the FT said in its online edition.

The deal, which would create the world's third-largest classified website, would also include Naspers investing $50 million in cash into Avito, giving it an 18.6 percent stake, the paper said.

After the deal Avito is likely to hold a 25 percent share of the Russian classified market in terms of traffic, the paper said.

No one was immediately available for comment at Naspers.

(Reporting by David Dolan; Editing by Ed Cropley)