WASHINGTON — The National Security Agency has secretly broken into the main communications links that connect Yahoo and Google data centers around the world, the Washington Post reported Wednesday, citing documents obtained from former NSA contractor Edward Snowden.

A secret accounting dated Jan. 9, 2013, indicates that NSA sends millions of records every day from Yahoo and Google internal networks to data warehouses at the agency's Fort Meade, Md., headquarters.

In the past 30 days, field collectors had processed and sent back more than 180 million new records — ranging from “metadata,” which would indicate who sent or received emails and when, to content such as text, audio and video, the Post reported Wednesday on its website.

The new details about the NSA's access to Yahoo and Google data centers around the world come at a time when Congress is reconsidering the government's collection practices and authority, and as European governments are responding angrily to revelations that the NSA collected data on millions of communications in their countries.

The NSA's principal tool to exploit the Google and Yahoo data links is a project called MUSCULAR, operated jointly with the agency's British counterpart, GCHQ. The Post said NSA and GCHQ are copying entire data flows across fiber-optic cables that carry information between the data centers of the Silicon Valley giants.

The NSA has a separate data-gathering program, called PRISM, which uses a court order to compel Yahoo, Google and other Internet companies to provide certain data. It allows the NSA to reach into the companies' data streams and grab emails, video chats, pictures and more.

U.S. officials have said the program is narrowly focused on foreign targets, and technology companies say they turn over information only if required by court order.