U.S. President Donald Trump accused former President Barack Obama of "treason" on Tuesday, accusing him, without providing evidence, of leading an effort to falsely tie him to Russia and undermine his 2016 presidential campaign.

Besides Obama, President Trump on Tuesday rattled off a list of people he accused of acting criminally "at the highest level."

Hours after Trump falsely accused Obama of trying to rig the 2016 election, the ex-president’s office said it had no choice but to publicly refute the claim.