Another major leak of top secret materials has again put America's top spies in hot water — while delivering a coup for anti-secrecy group WikiLeaks.

The group left the Central Intelligence Agency heavily bruised with the publication Tuesday of nearly 9,000 documents it said were only part of a huge trove of records, plans and malware code in its possession — purportedly the entire CIA hacking arsenal.

Adding insult to injury, WikiLeaks founder Julian Assange scolded the agency as extremely careless to have lost control of the materials — WikiLeaks said they got access to it via the circle of private contractors to US intelligence.

"This is a historic act of devastating incompetence, to have created such an arsenal and then stored it all in one place," Assange said.

President Donald Trump said the leak shows the agency's operations are "outdated" — and notably did not criticise WikiLeaks for baring US secrets.

It was the fourth major leak of top secret materials from US spy agencies in less than four years.

The CIA's sister spy body, the National Security Agency, was rocked in 2013 when contractor Edward Snowden released documents showing how it secretly raked up data on Americans' telecommunications and spied on US allies.

Early last year, a secretive hacking group called the Shadow Brokers offered for sale online a batch of hacking tools stolen from the NSA.

And in late 2016, the NSA discovered that another contractor, Harold Martin, had removed to his home an estimated 50 terabytes worth of data and documents, including reportedly sensitive hacking tools.

So far, there is no evidence that Martin's cache left his control, and the government charged him only with removing classified materials in violation of his contract.

The result, said security consultant Paul Rosenzweig, is "the continuing erosion in trust of and damage to the reputation to the American intelligence community." 

"Within the community now, everybody's looking over their shoulder," he said.

"Outside the community, frankly, if I were the British intelligence or French intelligence or Israeli intelligence…

I'd think twice before giving anything to the Americans." 

The WikiLeaks release has set off an intense probe into how the materials — which detailed how the CIA focuses on breaking into personal electronics like smartphones — got away from the agency.

The investigation could focus on whether the CIA was sloppy in its controls over private contractors it hires to help do work like creating and testing hacking tools.