(Reuters) The debate over whether the government is violating citizens' privacy rights while trying to protect them from terrorism escalated dramatically on Thursday amid reports that authorities have collected data on millions of phone users and tapped into servers at nine internet companies. The White House spent much of the day defending the National Security Agency's secret collection of telephone records from millions of Americans as a "critical tool" for preventing attacks, as critics called the program - first reported by Britain's Guardian newspaper - a heavy-handed move that raised new questions about the extent of the U.S. government's spying on its citizens. At day's end, the flap over the NSA's mining of data from customers of a subsidiary of Verizon Communications was overtaken by a Washington Post report that described an even more aggressive program of government surveillance. The Post reported that the NSA and the FBI have been tapping "directly" into the central servers of leading U.S. internet companies to gain access to emails, photographs, audio, video, documents, connection logs and other information that enable analysts to track a person's movements and contacts over time. Some of the companies named in the article - Google, Apple, Yahoo and Facebook - immediately denied that the government had "direct access" to their central servers. Microsoft said it does not voluntarily participate in any government data collection and only complies "with orders for requests about specific accounts or identifiers. James Clapper, the director of national intelligence, said the report contained "numerous inaccuracies." Washington Post spokeswoman Kristine Coratti said the paper stood by its report, which was based on an NSA document that it published online. Security Image