Donald Trump has lashed out at reports of his undisclosed encounter with Vladimir Putin at the G20 earlier this month, describing them as "sick".

The US and Russian leaders were in Germany for the summit, and came face-to-face for the first time at a two-hour meeting on July 7 – which was reported at the time.

It emerged on Tuesday that the pair had a second discussion, lasting about an hour, during a dinner for the Group of 20 heads of state and their spouses in Hamburg. The pair were joined only by Mr Putin's translator.

"Fake News story of secret dinner with Putin is 'sick'. All G 20 leaders, and spouses, were invited by the Chancellor of Germany. Press knew!," Mr Trump tweeted.