Greenwald: NSA and FBI spied on five Muslim-Americans
US spy agencies snooped on the emails of five high-profile Muslim Americans in an effort to identify security threats, documents leaked by fugitive ex-NSA contractor Edward Snowden show.
The targets include a lawyer, professor and a political operative, according to a report published in the Intercept.
The Intercept is an online news site overseen by Glenn Greenwald, who helped publish many of Mr Snowden's leaks.
The FBI and NSA said they only spied on Americans when they had probable cause.
"The National Security Agency and FBI have covertly monitored the emails of prominent Muslim-Americans... under secretive procedures intended to target terrorists and foreign spies," according to The Intercept report.
Those allegedly spied on include:
• Faisal Gill, a Republican Party operative and former Department of Homeland Security employee
• Asim Ghafoor, a lawyer who represented clients in terrorism-related cases
• Hooshang Amirahmadi, an Iranian-American professor at Rutgers University
• Agha Saeed, a former political science professor at California State University
• Nihad Awad, the executive director of the Council on American-Islamic Relations
According to the report - the result of a three-month investigation using classified documents obtained from Mr Snowden - all five individuals have denied involvement in terrorist activities.
The NSA and Department of Justice quickly responded to the report, saying emails of Americans are only accessed if there is probable cause.
"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," the agencies wrote in a joint statement.
The White House has ordered a review of national security agencies in the wake of the allegations, however.
"Upon learning of this matter, the White House immediately requested that the Director of National Intelligence undertake an assessment of Intelligence Community policies, training standards or directives that promote diversity and tolerance," White House national security spokeswoman Caitlin Hayden said on Wednesday.
"The use of racial or ethnic stereotypes, slurs, or other similar language" is not acceptable, she added.
Several dozen civil liberties groups have also spoken out against the allegations made in The Intercept report, urging US President Barack Obama to provide a full public accounting of domestic surveillance.
It is not the first time US agencies have been accused of snooping on Americans. Previous documents leaked by Mr Snowden indicate the electronic files of thousands of citizens were scanned by the NSA.
Last year, Mr Snowden - a former NSA contractor now residing in Russia - fed a trove of secret NSA documents to news outlets including the Washington Post and the Guardian, where Mr Greenwald worked.
The US Congress has attempted to curb online snooping in the wake of the snooping revelations, with the House of Representatives passing legislation to that effect in mid-June.
The measure, added to a $570bn (£335bn) defence spending bill, would bar the NSA from collecting Americans' personal online information without a warrant.
Earlier this year the House also passed the USA Freedom Act that would limit the NSA's bulk data collection and storage of some American landline telephone call records.