Barack Obama didn't act against Russia as he was sure of Hillary's win: Donald Trump

US President Donald Trump stepped up his criticism on Monday of former Democratic President Barack Obama's handling of alleged Russian interference in the 2016 U.S. presidential campaign, accusing his predecessor of collusion and demanding an apology from investigators.

Trump has increasingly lashed out over the ongoing investigations into Russia's role in the election and possible collusion by his campaign. The Republican president said Obama "colluded or obstructed," but gave no other details about his accusation.

"The reason that President Obama did NOTHING about Russia after being notified by the CIA of meddling is that he expected Clinton would win... and did not want to 'rock the boat.' He didn't 'choke,' he colluded or obstructed, and it did the Dems and Crooked Hillary no good," he wrote, referring to Democrats and Hillary Clinton, his rival in the presidential election.

The White House referred any questions about the Russia investigations to Trump's personal lawyer, Marc Kasowitz. Representatives for Kasowitz as well as for Obama did not immediately reply to requests for comment on Trump's latest statement. In a Fox News interview broadcast on Sunday, Trump said he had learned that Obama had known about the Russia issue long before the election but that he "did nothing about it."

Department of Justice Special Counsel Robert Mueller along with several congressional committees are probing alleged Russian meddling in the election last November and any possible ties to Trump's campaign or associates. The Obama administration formally accused Russia in October of a campaign of cyber attacks against Democratic Party organizations ahead of the Nov. 8 election. In December, Obama ordered intelligence agencies to review cyber attacks and foreign intervention in the election and to deliver a report before he left office on Jan. 20.

The intelligence agencies said in January they had concluded that Moscow tried to tilt the election in Trump's favor, including by hacking into senior Democrats' emails and leaking them.

The Kremlin has denied such meddling and Trump has denied any collusion. Following a weekend Washington Post report about the Obama administration's responses to Russia matter, the top Democrat on the U.S. House of Representatives Intelligence Committee, Adam Schiff, criticized the Obama administration on Sunday for not taking earlier and tougher action against Russia.

Trump has called the probes a witch hunt and on Monday he demanded an apology, saying in a Twitter message: "With 4 months looking at Russia... they have zero "tapes" of T (Trump) people colluding. There is no collusion & no obstruction. I should be given apology!"