Donald Trump and Barack Obama. Win McNamee/Getty Images President Donald Trump appeared to admit that Russia interfered in the 2016 US presidential election in a Friday night tweet in which he criticized Barack Obama for his handling of Russia's cybertattacks that were meant to swing the election away from Hillary Clinton.

"Just out: The Obama Administration knew far in advance of November 8th about election meddling by Russia. Did nothing about it. WHY," Trump asked.

The heads of several US intelligence agencies issued a statement formally accusing Russia of trying to interfere in the election on October 7 last year.

The FBI and several congressional committees are running multipronged investigations of possible cooperation between the Trump campaign and Russia and potential obstruction of justice by Trump. The president has repeatedly called the probe a "witch hunt" and a "phony story."

On Friday, Trump also said in an interview on Fox News' "Fox and Friends" that Obama "knew about Russia a long time before the election, and he did nothing about it."

"The CIA gave him information on Russia a long time before they even — before the election," Trump said. "To me — in other words, the question is, if he had the information, why didn't he do something about it? He should have done something about it."

Other Obama administration officials defended their efforts to counteract Russia's activities.