The group posted nearly 9,000 documents it said were leaked from the Central Intelligence Agency, in what it described as the largest-ever publication of secret intelligence materials.
WikiLeaks claimed that a vast trove of CIA documents, hacking tools and code representing "the majority of its hacking arsenal" were leaked within the cyber security community -- and that it had received, and released, a part of them.
"This extraordinary collection, which amounts to more than several hundred million lines of code, gives its possessor the entire hacking capacity of the CIA," it said, warning of a risk of cyber weapons proliferation.
Neither the CIA nor the White House would say if the documents were genuine.
If corroborated, the leak could represent a huge new embarrassment to US intelligence, adding to Edward Snowden's 2013 expose of National Security Agency spying on Americans' communications, and the arrest last year of an NSA official for removing massive amounts of top-secret material to his home over 20 years.
WikiLeaks said the data shows that the CIA is now rivaling the NSA, the US government's main electronic spying body, in cyber warfare, but with less oversight.
- Bypassing encryption -
The archive shows the CIA exploiting weaknesses it discovers in hardware and software systems, including those made by US companies -- without letting anyone know about the flaws in question.
Documents show the CIA has produced more than 1,000 malware systems -- viruses, trojans and other software that can infiltrate and take control of personal electronics, WikiLeaks noted.
These hacking tools have targeted iPhones, Android systems such as the personal phone reportedly still used by President Donald Trump, popular Microsoft software, and Samsung smart TVs, which can be transformed into covert microphones, according to WikiLeaks.
The agency has also examined hacking into the electronic control systems on cars and trucks, potentially enabling it to control them remotely.
By infecting and effectively taking over the software of smartphones, WikiLeaks said, the CIA can get around the encryption technologies of popular apps like WhatsApp, Signal, Telegram, Weibo, and Confide by collecting communications before they are encrypted.
- 'Looks authentic' -
The CIA would neither confirm nor deny the documents were genuine.
"We do not comment on the authenticity or content of purported intelligence documents," said spokesman Jonathan Liu in an email.
But Devin Nunes, chairman of the House of Representatives's Intelligence Committee, said the disclosures "appear to be very, very serious."
"We are very concerned," he said.
The documents allegedly come from the CIA's Center for Cyber Intelligence, which operates both from its Langley, Virginia, headquarters near Washington, and from an office in the US consulate in Frankfurt, Germany, according to WikiLeaks.
"The archive appears to have been circulated among former US government hackers and contractors in an unauthorized manner, one of whom has provided WikiLeaks with portions of the archive," the group said.
Snowden, who was a contract employee for the NSA before he stole and leaked secret materials, said via Twitter that the document trove "looks authentic."
- Cyber weapons 'proliferation' -
WikiLeaks said the documents' leak suggests that the CIA has not sufficiently controlled its own cyber weapons, potentially permitting them to fall into the hands of other hackers.
Cindy Cohn, executive director of the Electronic Frontier Foundation, blasted the CIA for not helping companies plug the security gaps in their devices.
"The dark side of this story is that the documents confirm that the CIA holds on to security vulnerabilities in software and devices -- including Android phones, iPhones, and Samsung televisions -- that millions of people around the world rely on," she said in a statement.
"As these leaks show, we're all made less safe by the CIA's decision to keep -- rather than ensure the patching of -- vulnerabilities."
The release showed WikiLeaks's readiness to continue publishing secret material on the United States despite having been severely criticized in Washington for last year's leaks of materials that damaged Democrat Hillary Clinton's presidential bid.
US intelligence officials said in January that WikiLeaks had knowingly or unknowingly become a tool of a high-level Russian operation to interfere in the US election with those disclosures.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)