The National Security Agency collected evidence of online sexual activity and visits to pornographic websites as part of a proposed plan to harm the reputations of six people the agency considered "radicalisers," the Huf-fington Post reported, citing documents released by former NSA contractor Edward Snowden.

The targets, all Muslims, are described in the document as examples of how "personal vulnerabilities" can be learned through electronic surveillance, and then exploited to undermine a target's credibility, reputation and authority, the Post said in its report.

Among the vulnerabilities are "viewing sexually explicit material online" and "using sexually explicit persuasive language when communicating with inexperienced young girls," according to the NSA document, dated October 3, 2012.

None of the six individuals targeted by the NSA is accused in the document of being involved in terror plots. The agency believes they all currently reside outside the United States, Huffington Post reported.

However, the agency identifies one of them as a "US person," which means he is either a US citizen or a permanent resident. A US person is entitled to greater legal protections against NSA surveillance than foreigners are, the report noted.

"The NSA scandal turns a dangerous corner," Ben Wizner, director of the ACLU Speech, Privacy & Technology Project, wrote on Twitter after reading the report. "I bet Washington is full of nervous people."

The latest revelations come as the European Union reviews a commercial data-sharing agreement with the US known as Safe Harbor. One EU executive threatened to freeze the pact, which covers commercial swaps between US and European companies, information exchanged to limit international terrorist funding, and the supply of information on transatlantic air passengers.

Huffington Post released an appendix that was attached to the document which lists the argument each surveillance target has made that the NSA says constitutes radicalism, as well the personal "vulnerabilities" the agency believes would leave the targets "open to credibility challenges" if exposed.

One target's offending argument is that "Non-Muslims are a threat to Islam," and a vulnerability listed against him is "online promiscuity."

Another target, a foreign citizen the NSA describes as a "respected academic," holds the offending view that "offensive jihad is justified," and his vulnerabilities are listed as "online promiscuity" and "publishes articles without checking facts."

The Huffington Post said it withheld the names and locations of the six people and noted that the allegations made by the NSA about their online activities in the document cannot be verified.