The FBI and National Security Agency have monitored the emails of prominent Muslim-American activists, academics and a political candidate, according to a report co-authored by journalist Glenn Greenwald.
The report appearing in the online news site The Intercept said the surveillance was authorised by a secret intelligence court under procedures intended to locate spies and terrorist suspects.
The report, citing documents in an NSA spreadsheet leaked by former contractor Edward Snowden, showed the emails of the individuals, but not their names.
They were Faisal Gill, a longtime Republican Party operative and one-time candidate for public office; Asim Ghafoor, a lawyer who has represented clients in terrorism-related cases; Hooshang Amirahmadi, an Iranian-American professor at Rutgers University; Agha Saeed, a civil liberties activist and former professor at California State University; and Nihad Awad, the executive director of the Council on American-Islamic Relations.
According to the report by Greenwald and Murtaza Hussain, the spreadsheet shows 7485 email addresses listed as monitored between 2002 and 2008.
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Many of the emails appeared to belong to foreigners suspected of being linked to al-Qaeda.
But the journalists' investigation also found a number of US citizens monitored in this manner, which requires an order from the secret intelligence court based on evidence linking them to espionage or terrorist activities.
US officials, responding to the report, said communications are only monitored with a "legitimate foreign intelligence or counterintelligence purpose".
"It is entirely false that US intelligence agencies conduct electronic surveillance of political, religious or activist figures solely because they disagree with public policies or criticise the government, or for exercising constitutional rights," said a joint statement from the Justice Department and office of the Director of National Intelligence.
"Unlike some other nations, the United States does not monitor anyone's communications in order to suppress criticism or to put people at a disadvantage based on their ethnicity, race, gender, sexual orientation or religion."
