The National Security Agency gathers nearly 5 billion records a day on the location of mobile telephones worldwide, including those of some Americans, the Washington Post reported on Wednesday, citing sources including documents obtained by former NSA contractor Edward Snowden.
The records feed a database that stores information about the locations of "at least hundreds of millions of devices," the newspaper said, according to the top-secret documents and interviews with intelligence officials.
The report said the NSA does not target Americans' location data intentionally, but acquires a substantial amount of information on the whereabouts of domestic cellular telephones "incidentally."
One manager told the newspaper the NSA obtained "vast volumes" of location data by tapping into the cables that connect mobile networks globally and that serve U.S. cellphones as well as foreign ones.
U.S. intelligence officials contacted by Reuters declined to comment on the Post report.
The article cited officials as saying the programs that collect and analyze location data are lawful and meant solely to develop intelligence on foreign targets.
U.S. intelligence agencies' extensive collection of telephone and Internet data has been subject to scrutiny since Snowden began leaking information in June showing that surveillance was far more extensive than most Americans had realized.
Facing a public outcry and concern that programs are targeting average Americans as well as international terrorism suspects, Republican and Democratic members of Congress are writing legislation to clamp down on the data collection and increase public access to information about it.
Advocates responded to the Post report by calling on Congress to take up legislation to reform NSA data-gathering programs.
"How many revelations of NSA surveillance will it take for Congress to act? Today's news is the latest startling blow to the right to privacy," Zeke Johnson, director of Amnesty International USA's Security and Human Rights, said in a statement.