WASHINGTON (REUTERS) - President Donald Trump is striking back against reports that his campaign aides spoke extensively with Russian spies during last year's election. These are revelations that raise new alarms about Moscow's alleged meddling in the US presidential race.

The New York Times on late Tuesday night (Feb 14) cited four current and former US officials that are members of Trump's campaign and other associates who had repeated contacts with senior Russian intelligence officials in the year before the election.

At a news conference with visiting Israeli Prime Minister Benjamin Netanyahu, Trump slammed what he called illegal leaks from the US intelligence community.

"And it's been going on for a long time, before me, and now it's really going on. People are trying to cover up for a terrible loss that the Democrats had under Hillary Clinton," Trump said.

These alleged contacts are separate from the back channels calls Flynn made to the Russian ambassador before he took office, which led to his quick departure from the White House.

On Monday, White House spokesman Sean Spicer said Flynn had left because he had lost the trust of the president, but on Tuesday, Trump took a very different line.

"Michael Flynn, General Flynn, is a wonderful man. I think he's been treated very, very unfairly by the media," said Trump.

Sources tell Reuters that Trump has asked Vice-Admiral Robert Harward to serve as national security adviser, replacing Flynn.

Pressure is mounting on Capitol Hill as Republicans promise to get to the bottom of Trump's Russia ties, calling for Flynn to testify before Congress.