U.S. President Donald Trump on Wednesday defended Donald Trump Jr., declaring his innocence following revelations in emails that showed his eldest son welcomed Russia’s help against his father’s rival in last year’s presidential election.

“My son Donald did a good job last night,” Trump wrote on Twitter, referring to a television interview by his son late Tuesday on the issue.

“He was open, transparent and innocent. This is the greatest Witch Hunt in political history. Sad!” he continued.

It comes after Tim Kaine, Hillary Clinton’s running mate in the election, said: “This is moving into perjury, false statements and even potentially treason.

“This should have set off alarm bells and red lights and instead, what it seemed to do is it activated their salivary glands. They should have turned this over to law enforcement immediately.”

While experts have said his actions could not be categorised as treason, some attorneys say that the events described in the emails could amount to a conspiracy to break campaign finance law.

Russian Foreign Minister Sergei Lavrov said on Wednesday it was “wild” that Mr. Trump’s eldest son was blamed for meeting a Russian lawyer that emails show might have had damaging information about Hillary Clinton last year.

“I learned with surprise that a Russian lawyer, a women, is being blamed and Trump’s son is being blamed for meeting. For me, this is wild,” Lavrov said during a visit to Brussels.

“Because when any person speaks to a lawyer, what problem or threat could be there? I didn’t know about this, I learned about it from television.”