Authorities are scrambling after sensitive US intelligence documents leaked online. 

Last month, highly classified Pentagon documents appeared online, exposing the extent of US eavesdropping on key allies, including South Korea, Israel, and Ukraine. 

These documents, which are said to be authentic, have left US officials deeply worried about the revelations and fear that they could jeopardise sensitive sources and compromise important foreign relationships. 

The leak has also led the Pentagon to take steps to tighten the flow of such highly sensitive documents, which are normally available on any given day to hundreds of people across the government. 

While spying is a central part of how the US intelligence community collects information globally, diplomats from some of the countries mentioned have expressed frustration and concern about the leak. 

US allies are now doing damage assessments, scrambling to determine whether any of their own sources and methods have been compromised. 

Members of the Five Eyes intelligence-sharing arrangement with the US, including Australia, reportedly expect the US to share a damage assessment with them in the coming days. News outlet CNN says it has reviewed 53 leaked documents, all of which appear to have been produced between mid-February and early March. 

One of the documents revealed that the US has been spying on Ukrainian President Volodymyr Zelensky. Ukrainian officials are deeply frustrated about the leak, according to reports.