The U.S. military armed and trained members of a dissident Iranian opposition group during the Bush administration, according to a report published Friday in The New Yorker.

The report claims members of the Mujahideen-e-Khalq organization were provided with extensive training by the U.S. Defense Department's Joint Special Operations Command (JSOC). The training sessions were allegedly conducted in secret at a site belonging to the U.S. Department on Energy in Nevada.

The organization, also known as the MEK or the People's Mujahedin of Iran, was originally founded by leftist university students as an Islamist-Marxist group in 1965. It later staged attacks against the Islamic Republic from within Iraq, under Saddam Hussein.

According to the report, the training of MEK operatives was conducted as part of the Bush administration's global war on terror, and ended before Barack Obama took office.

Sources quoted in the article said the MEK operatives were taught how to intercept telephone conversations and text messages inside Iran, which were then translated and shared with American intelligence officials.

Other sources confirmed a previous report in March by NBC News, which alleged that Israel's Mossad was also involved in financing and training MEK units, with the goal of targeting Iranian nuclear enrichment facilities and power plants.

While it claims to have renounced violence several years ago and is today part of a coalition of exiled Iranian anti-regime groups, the organization is still classified as a terrorist organization by the U.S. State Department. The EU removed it from its list of terrorist organizations in 2009.

U.S. officials denied that American forces had been involved in training the MEK.