President-elect Donald Trump has rejected as “ridiculous” a CIA assessment that Russian hackers tried to sway the election in his favour.

He told Fox News the Democrats were putting out the reports because they were embarrassed at the scale of the election defeat.

This came as a bipartisan quartet of high-profile senators said Sunday that “recent reports of Russian interference in our election should alarm every American,” as President-elect Donald Trump sharpened his unprecedented attacks on US intelligence agencies.

The group  called for an investigation into American intelligence agencies’ conclusion that Russian hacking was intended to help Trump defeat Hillary Clinton.

On Friday, CIA officials told US media they had concluded that Russians hackers were trying to help Mr Trump.

Russian officials have repeatedly denied the hacking accusations.

Mr Trump said it might have been Russia but it was impossible to know.

“They have no idea if it’s Russia or China or somebody sitting in a bed some place,” he said.

President Barack Obama has ordered a complete review of the hacks, which targeted emails at the Democratic Party and the emails of a key aide to presidential nominee Hillary Clinton.

The contents of the emails, passed to Wikileaks and posted online, were embarrassing to the Democrats and shook up the presidential campaign.

Trump again signaled Sunday a willingness to confront Beijing, questioning whether the United States should keep its long-standing position that Taiwan is part of “one China.”