Twitter has handed over to Senate investigators the profile names of 201 accounts linked to Russian attempts at influencing the 2016 presidential election.

Twitter told congressional investigators it has suspended at least two dozen accounts that may have been tied to Russia, but the information shared by the social media giant at the briefing was described as "frankly inadequate".

President Donald Trump had a second, previously undisclosed conversation with Russian President Vladimir Putin at a summit in Germany earlier this month.

The special counsel appointed to investigate Russian influence in the 2016 US presidential campaign is now examining whether Donald Trump tried to obstruct justice, according to a report.