Law enforcement and intelligence services in the US have been collaborating to investigate possible Russian money covertly be used to aide the Trump campaign for months, McClatchy reported.

Two sources told McClatchy that the FBI, CIA, NSA, Justice Department and the Treasury Department's Financial Crime Enforcement Network have been involved in an inquiry that started in spring 2016, long before allegations of Russian links to Trump were gathered by a former MI6 agent and released in an unverified document by Buzzfeed.

The McClatchy investigation had been looking at whether money could have secretly been sent by the Kremlin to pay hackers through a system that pays Russian-American pensioners. A report by the US intelligence agencies concluded in early January that Putin had personally ordered attempts to influence the US election in Trump's favour.