An online news site reported Wednesday that U.S. intelligence and law-enforcement agencies monitored the e-mails of several prominent Muslim American activists and lawyers, prompting cries of protest from civil liberties advocates and a strong rebuttal from the government.

A lengthy article published on the Intercept stated that the National Security Agency and the FBI monitored the e-mails of five Muslim Americans under procedures meant to target foreign terrorists and spies.

The surveillance, according to the article, apparently was conducted under the Foreign Intelligence Surveillance Act, which requires the government to have probable cause to believe that the American targets are agents of foreign powers or terrorists. The article stated that it was unclear whether warrants were obtained and what the justification for the targeting was.

The Intercept article said the five men denied any involvement in terrorism or espionage and that none advocated violent jihad or are known to have been implicated in a crime. It quoted some of them as saying they believed they had been targeted because they were of Muslim heritage.

The piece, which resulted from a three-month investigation, elicited claims that the government was conducting surveillance that violated people's constitutional rights.

"It is entirely false that U.S. intelligence agencies conduct electronic surveillance of political, religious or activist figures solely because they disagree with public policies or criticize the government, or for exercising constitutional rights," the Office of the Director of National Intelligence (ODNI) and the Justice Department said in a joint statement.

The article was based on documents leaked by former NSA contractor Edward Snowden.