US President Donald Trump and Russian President Vladimir Putin had a second undisclosed meeting at the G20 summit that reportedly lasted for an hour.

The only other person at the meeting on the sidelines of the gathering of world leaders in Hamburg was Putin's official interpreter, multiple reports have said.

IBTimes UK reached out to the White House for comment but did not receive a response by the time of publication.

The Washington Post reported that the conversation took place during a dinner for G20 leaders when Trump left his seat to sit beside the Russian president.

The two leaders also held an already publicised two hour meeting during the summit as well.

The meeting was first reported publicly by Ian Bremmer, the president of the consulting firm Eurasia Group.

"We clearly know that Trump does not care what the media has to say about his desire to have a close personal relationship with the Russian president and what drives it," Bremmer told Charlie Rose.

"Never in my life as a political scientist have I seen two countries, major countries, with a constellation of national interests that are as dissonant while the two leaders seem to be doing every possible to make nice-nice and be close to each other." Bremmer said.

The Trump administration has been dogged by accusations of campaign collusion with Russia, the latest chapter of which unfolded after Trump's eldest son, Donald Trump Jr, tweeted out an email chain that seemed to confirm he attended a meeting with a Kremlin-linked lawyer in hopes of getting damaging information of his father's presidential rival, Hillary Clinton.

US intelligence agencies have previously said that high level Russian official ordered attempts to influence the presidential election in Trump's favour.