Donald Trump lashed out at a journalist during a White House press conference, blasting some media outlets as "corrupt".

The press conference was with Finnish President Sauli Niinistö, but the questions largely focused on the unfolding whistleblower complaint and the impeachment inquiry launched against the US President following revelations he asked Ukraine's leader Volodymyr Zelensky for help investigating Democratic 2020 candidate Joe Biden.

Jeff Mason, White House correspondent for Reuters and the former president of the White House Correspondents Association, asked Trump what he wanted the Ukrainian President to do about the Bidens.

President Donald Trump speaks during a news conference with and Finnish President Sauli Niinisto at the White House in Washington. (Photo / AP)

He initially fobbed off the question, then said to the reporter: "Are you talking to me?"

Mason said: "Yes, it is just a follow-up of what I just asked you, sir."

Trump replied: "We have the president of Finland. Ask him a question."

"I have one. I just wanted to follow up on the one I asked you," Mason said.

"Did you hear me? Ask him a question. I have given you a long answer. Ask this gentleman a question. Don't be rude," said Trump.

"No sir. I don't want to be rude. I just wanted you to have a chance to answer the question I just asked you," Mason responded.

Trump engages in contentious back and forth with @JeffMason1 after he dodges Ukraine question:

Trump: We have the president of Finland, ask him a question.

Mason: I have one for him, I just wanted to follow up on the one I asked you—

Trump: Did you hear me? Ask him a question! pic.twitter.com/Co64SmxOmk

— Oliver Darcy (@oliverdarcy) October 2, 2019

Mr Trump then made accusations of treason, slamming the "corrupt media" as "truly the enemy of the people".

"I answered everything," Trump said. "It's a whole hoax, and you know who is playing into the hoax, people like you and the fake news media that we have in this country, and I say in many cases, the corrupt news media. Because you are corrupt. Much of the media in this country is not just fake, it's corrupt. And you have some very fine people too. Great journalists. Great reporters. But to a large extent, it is corrupt and it is fake."

At the end of the press conference, Mason said he was just trying to get an answer to his question. He eventually tried to move on to another question, but Trump cut him off, saying: "You never had wins with other presidents, did you? Your wins are now."

Niinistö interjected: "But I think the question is for me?"

Trump berates @jeffmason1 after Mason presses him to actually answer the question he asked (he never does). The Finnish president can't help but chuckle at the shit show. pic.twitter.com/Uc6G4HvE7r

— Aaron Rupar (@atrupar) October 2, 2019

During his opening statement, Niinistö told Trump: "Mr President, you have here a great democracy. Keep it going on."

The remark sparked speculation online over whether the Finnish leader was being genuine or sarcastic in the context of his outburst at the journalist:

The Finnish president just said to Trump, “You have a great democracy. Keep it going on.” Is he subtweeting Trump to his face?!

— Daniel W. Drezner (@dandrezner) October 2, 2019

“Mr. President, you have here a great democracy. Keep it going on.” -Finnish President Sauli Niinistö, becoming one with the concept of sarcasm during a joint press conference with President Insanity.

— Dennis Detwiller (@drgonzo123) October 2, 2019

The only Finnish journalist who got to ask a question asked Mr Niinistö: "What kind of favours has Trump offered you?"

It appeared to be a reference to the Ukraine phone call scandal, but Trump did not address it, saying: "I think you mean the other way around."