Glenn Greenwald, the American journalist who published documents leaked by fugitive former US intelligence contractor Edward Snowden, plans to make new revelations "within the next 10

days or so" on secret US surveillance of the Internet.

"The articles we have published so far are a very small part of the revelations that ought to be published," Greenwald on Tuesday told a Brazilian congressional hearing that is investigating the US internet surveillance in Brazil.

“There will certainly be many more revelations on spying by the U.S. government and how they are invading the communications of Brasil and Latin America," he said in Portuguese.

The Rio de Janeiro-based colum-nist for Britain's Guardian newspaper said he has recruited the help of experts to understand some of the 15,000 to 20,000 classified documents from the National Security Agency that Snowden passed him, some of which are "very long and complex and take

time to read."

Greenwald told Reuters he does not believe the pro-transparency website WikiLeaks had obtained a package of documents from Snowden, and that only he and filmmaker Laura Poitras have complete archives of the leaked material.

After a meeting in June with Snowden in Hong Kong, Greenwald published in The Guardian the first of many reports that rattled the US intelligence community by disclosing the breadth and depth of alleged NSA surveillance of telephone and internet usage.