The Wall Street Journal, citing current and former NSA officials, said that the agency works with telecom companies to intercept communications that originate or end abroad, or are entirely foreign but pass through the US.

The NSA keeps the content of some emails between US citizens, along with filtering domestic phone calls made over the internet, according to the Journal's report, which was released late Tuesday local time.

Officials told the newspaper that the broad nature of the surveillance programs means that entirely domestic communications are more likely to be intercepted and collected. These surveillance programs show the NSA can track almost anything that happens online, so long as it is covered by a broad court order, the Journal said.

In responding to a request for comment made by the Reuters news agency, the NSA said its mission "is centered on defeating foreign adversaries who aim to harm the country."

"We defend the United States from such threats while fiercely working to protect the privacy rights of US persons," the agency said in an email. "It's not either/or. It's both."

The details of the US government's far-reaching surveillance programs were first revealed earlier this year by whistle-blower Edward Snowden, a former NSA contractor.

dr/hc (Reuters, dpa)