Donald Trump's adviser and son-in-law Jared Kushner met with Russian ambassador Sergey Kislyak, the White House said on Thursday – in just the latest explosive revelation about a growing list of contacts between Trump associates and the Kremlin.

Kushner, the husband of Ivanka Trump who the president brought in as a top White House advisor, met with the Russian ambassador inside Trump Tower in December, the New York Times reported Thursday.

Also in on the meeting was Lt. Gen. Mike Flynn, who stepped down as national security advisor after revelations about his contacts with Kislyak as Trump prepared to take office.

At the time Trump Tower was the unofficial White House, and every coming and going was in public - except those which the Trump transition team organized to keep under wraps.

Kislyak, regarded as one of Russia's most important spies, was therefore smuggled in by the Trump team for the meeting.

President Trump's son-in-law, Jared Kushner, met with Russia's ambassador to the U.S. in December, it was reported Thursday. Kushner was at the President's side Thursday on a trip to Newport, VA, and then with him when he returned to the Oval Office

Plenty of reporters in the lobby: Trump Tower was staked out by scores of reporters from dawn every day in December - but Russia's most senior diplomat, a man believed to be its top spy, was smuggled in by Jared Kushner

It is unclear where they met, but it is known that Kushner and Flynn had offices a floor below the one used by the then-president-elect.

'They generally discussed the relationship and it made sense to establish a line of communication,” White House spokeswoman Hope Hicks told the Times.

“Jared has had meetings with many other foreign countries and representatives — as many as two dozen other foreign countries’ leaders and representatives,' she added.

Trump has tasked Kushner with spearheading a host of complex issues, including Middle East peace initiatives.

But his contacts with Kislyak – who intelligence figures are said to regard Kislyak as a recruiter of intelligence assets – bring Kremlin contacts even closer to home.

The high-rise get together lasted about 20 minutes, Hicks said. Kushner hasn't met with him since, she said.

There was no mention of the meeting with the Kremlin big in the president-elect's public schedule, or in the reports compiled by pool reporters who set up camp in the lobby of Trump Tower from the November election until Trump took office.

The White House put out the information on a day when Attorney General Jeff Sessions announced he was recusing himself from any investigations related to the presidential elections – hours after it was reported that he met with Kislyak two times during the presidential campaign season.

One meeting occurred inside Sessions Senate office this fall.

'My staff recommended recusal. They said that since I had involvement with the campaign I should not be involved in any campaign investigation,' Sessions told reporters in a hastily-called press conference in the Department of Justice.

Before the press conference, Trump was asked if he knew Jeff Sessions had met Russia's ambassador before the election - and said: 'I wasn't aware at all.'

President Donald Trump says he has 'total' confidence in his attorney general and does not think he should recuse himself from Justice Department investigations involving Russia - but offered a lukewarm endorsement of his truthfulness

Not quitting: Jeff Sessions said he would sit out any decision on prosecutions which could arise from current investigations into whether Russia meddled in the election - but that he had not lied to the Senate

The president's intervention came as Sessions faced a firestorm over whether he lied to the Senate during confirmation hearings by failing to disclose his two meetings last summer with Vladimir Putin's man in Washington.

Asked as he visited the USS Gerard R. Ford in Newport News, Virginia, Trump was asked if Sessions told a Senate panel the truth about the communications. He gave only a half-hearted endorsement.

'I think he probably did,' Trump said.

Flynn left the White House after just weeks on the job after it was revealed he had multiple contacts with Kislyak where the Russia sanctions were discussed.

The Obama administration expelled 35 Russian diplomats in the waning days of the administration, following intelligence agency conclusions that Moscow backed U.S. election hacking.

It isn't just close Trump associates who met with the Russian ambassador, though Kushner, Flynne, and Sessions were among the most plugged-in Trump advisors.

Democratic Senators Dianne Feinstein of California and Claire McCaskill of Missouri were revealed to have met with the ambassador in the past.