THE HAGUE - The United States spied on the Netherlands from 1946 to 1968, the Dutch NRC newspaper quoted Snowden documents as showing on Saturday.

It was not clear who was bugged, when it was or with what intentions. Whether the spying stopped after 1968 was unclear either, according to documents of the US National Security Agency (NSA) leaked by former contractor Edward Snowden.

The NSA wanted to keep the tapping secret for the fear that the relationship between the Netherlands and the United States could be jeopardized, according to the documents.

In October, the NSA admitted monitoring mail and phone traffic in the Netherlands but denied considering the country a "target."

Dutch Interior Minister Ronald Plasterk confirmed the exchange of data between the Dutch intelligence service and the NSA, but condemned the interception of phone calls and mails without permission.

The documents also show that other US allies such as Belgium, Germany, France and Norway were also bugged as from 1946.

In addition, the documents revealed that the NSA had infected more than 50,000 computer networks worldwide by mid-2012 with malicious software designed to steal sensitive information.

Operations of the software were especially carried out in, among other nations, China, Russia, Venezuela and Brazil.