Washington, February 1 (RHC)-- Documents obtained by U.S. whistleblower Edward Snowden have revealed more about U.S. spying activities after Washington's spy chief James Clapper called on him to return all of the remaining unpublished documents.

The latest documents, which were published by The Huffington Post and the Danish daily newspaper Information, show that the U.S. National Security Agency monitored the communications of other governments prior to and during the Copenhagen Climate Summit in 2009.

According to the documents, which were marked 'top secret' at some points, “analysts here at NSA, as well as our Second Party partners, will continue to provide policymakers with unique, timely, and valuable insights into key countries' preparations and goals for the conference, as well as the deliberations within countries on climate change policies and negotiation strategies.”

'Second Party partners' refers to the five English-speaking countries known as the 'Five Eyes' club, which is an intelligence sharing alliance including the U.S., Canada, Britain, Australia and New Zealand.

The latest revelation has expanded the list of international events where the United States has intercepted the communications of other governments as other documents leaked by Snowden have already shown that the U.S. spied on the 2010 G-8 and G-20 summits in Toronto as well as the 2009 G-20 summit in London with the help of the host countries' governments.