The United States voiced renewed concern over the risks to individuals after the anti-secrecy site WikiLeaks made public more US diplomatic cables, many of which contained the names of sensitive sources.
State Department spokeswoman Victoria Nuland would not confirm the authenticity of the latest documents, but said "the United States strongly condemns any illegal disclosure of classified information.
"In addition to damaging our diplomatic efforts, it puts individuals' security at risk, threatens our national security and undermines our effort to work with countries to solve shared problems," Nuland told reporters.
"We remain concerned about these illegal disclosures and about concerns and risks to individuals," she said.
"We continue to carefully monitor what becomes public and to take steps to mitigate the damage to national security and to assist those who may be harmed by these illegal disclosures to the extent that we can," Nuland said.
Nuland was alluding to a policy that experts said involved US efforts to come to the aid of sources who ran the risk of being exposed, including possibly relocating them.
The New York Times reported that the latest dump of 133,887 confidential and secret documents included many containing the names of sensitive sources who could be at risk of reprisals if they were known to be talking to US diplomats.
Meanwhile in Australia officials were lambasting the whistle-blowing site for its "incredibly irresponsible" move to publish secret US cables that detailed Australians with suspected links to Yemeni terrorism.
Australia's Attorney-General Robert McClelland also noted contrary to previous efforts to redact identifying features, this "has not occurred in this case".
In a Twitter message the anti-secrecy website said only that it was "totally false that any WikiLeaks sources have been exposed or will be exposed".
However, in sampling half a dozen cables written between 2003 and 2009 where the author wrote "protect source," AFP observed that only one of them had the name of the source removed.
WikiLeaks meanwhile also said late Tuesday it was fending off a cyberattack after being lambasted for releasing more supposedly confidential US diplomatic cables.
"WikiLeaks.org is presently under cyberattack," the organization said in a terse message on microblogging service Twitter.
After WikiLeaks obtained around 250,000 cables and released the first batch of them in November last year, the US State Department has been exposed to embarrassing revelations about how it viewed foreign government officials.
Diplomats worried the disclosures would make it harder to do their work because officials, representatives of non-government organizations, activists and others would hesitate to talk to them privately for fear of being exposed.
However, experts said WikiLeaks was much more careful about editing out the names of US government sources in the first batch of released documents.
That is not the case in the latest batch, according to Steven Aftergood, a specialist on government secrecy at the Federation of American Scientists who reviewed dozens of cables and found only one case where the source was removed.
"It's a worrisome development particularly because a number of the confidential sources are not public officials but are private contacts, members of NGOs, or private firms," Aftergood told AFP.
"And in several cases, the cables themselves have specified that the sources need to be protected," he said.
He said the consequences for the sources range from losing the confidence of the people they usually deal with to actually losing their jobs. "In some extreme cases," he added, they may be in "personal jeopardy."
"The point is that they (WikiLeaks) have changed their practice and that the kinds of information that they were redacting as recently as a few months ago is now being put out in the open," Aftergood said.
For former State Department spokesman Philip Crowley, the problem with the leaks was not about embarrassing revelations as much as "about the risk to lives and careers of individuals" who have helped US diplomats understand events.
Crowley, who now has a prestigious university teaching post in Pennsylvania, said he does not know if WikiLeaks founder Julian Assange is right in saying that nobody has died from a WikiLeaks disclosure.
"That's not the only measure. There have been people forced to move, people who have lost their careers, people who simply are much more cautious," he said.