Governor Ralph Northam clung to office on Sunday amid nearly unanimous calls from his own party to resign over a racist photo in his 1984 medical school yearbook, going silent after a bizarre 24 hours in which he first admitted he was in the picture, then denied it.

The Democrat's stunning about-face at a weekend news conference where he also acknowledged putting on blackface for a dance contest decades ago and appeared to briefly entertain the notion of doing the Michael Jackson moonwalk for reporters only seemed to make things worse.

The chairwoman of the Congressional Black Caucus declared that Northam "still does not understand the seriousness of his actions". The photo shows someone in blackface and another person in a Ku Klux Klan hood and robe.

"I think he's been completely dishonest and disingenuous," Rep. Karen Bass, D-California, said on NBC's 'Meet the Press'. "He knew this picture was there, and he could've come clean and talked to African-Americans that he's close to decades ago."

Northam worshipped at his home church, the predominantly black First Baptist in Capeville, but otherwise kept out of sight on Sunday as calls intensified for him to step down.

A Northam official, who was not authorised to speak on the record, said the governor met with minority officials in his administration on Sunday evening. It wasn't immediately known what was discussed and the official spoke on condition of anonymity.

Even if Northam doesn't resign, the scandal threatens to cripple his ability to govern. He has lost the support of virtually all of the state's Democratic establishment.

Top Republicans in the Virginia General Assembly also urged Northam to step down, as did many declared and potential Democratic presidential candidates.

Virginia governors can be removed for "malfeasance in office, corruption, neglect of duty, or other high crime or misdemeanour" under the state constitution, but top Democrats said they don't believe it will come to that.

Former Virginia Governor Terry McAuliffe predicted that Northam who served as McAuliffe's lieutenant governor will eventually leave office.

"Ralph will do the right thing for the Commonwealth of Virginia," McAuliffe said Sunday on CNN's 'State of the Union'. Northam apologised on Friday for appearing in the photograph on his yearbook page.

He did not say which costume he was wearing, but said he was "deeply sorry for the decision I made to appear as I did in this photo". On Saturday, though, the governor reversed course and said the picture "is definitely not me".

While talking with reporters, Northam admitted he once used shoe polish to put on blackface as part of a Michael Jackson costume for a 1984 dance contest in Texas, when he was in the Army. Northam said he regrets that he didn't understand "the harmful legacy of an action like that".

Asked by a reporter if he could still do Jackson's famous moonwalk, Northam looked at the floor as if thinking about demonstrating it. His wife put a stop to it, telling him, "Inappropriate circumstances."

His shifting explanations did little or nothing to sway prominent Democrats who had swiftly disowned him.

Both of Virginia's US senators, Mark Warner and Tim Kaine, joined the dean of Virginia's congressional delegation, Rep. Bobby Scott, in saying they no longer believe Northam can serve effectively.

James Ryan, president of the University of Virginia, said in a statement that it would be "exceedingly difficult" for Northam to continue serving.

If Northam does resign, Lt. Gov. Justin Fairfax would become the second African-American governor in the state's history. He stopped short of calling for Northam's departure but said he "cannot condone actions" from Northam's past that "suggest a comfort with Virginia's darker history of white supremacy, racial stereotyping and intimidation". McAuliffe faulted Northam's handling of the furore.

"If it wasn't him in the photo, he should've said that on Friday," McAuliffe said. "Instinctively, you know if you put black paint on your face. You know if you put a hood on. And so if it isn't you, you come out immediately and say, 'This is not me.'"

Ultimately, McAuliffe said, "It doesn't matter whether he was in the photo or not in the photo at this point. We have to close that chapter. We have to move Virginia forward."

One of the few voices backing Northam on Sunday was former Virginia Rep. Jim Moran, a Democrat who served in Congress from 1991 to 2015.

Moran told ABC's 'This Week' that Northam's record including his support of Medicaid expansion and of public schools in minority neighbourhoods shows that the embattled governor is a friend of African-Americans and that he should ride out the storm.

"I think it is a rush to judgement before we know all of the facts and before we've considered all of the consequences," said Moran, who is white. "I don't think these public shamings really get us all that much."

Northam, a paediatric neurologist who came to politics late in life, spent years courting the black community in the run-up to his 2017 race for governor.

He recently came under fire from Republicans who have accused him of backing infanticide after he said he supported a bill loosening restrictions on late-term abortions.

Late last month, Florida's secretary of state resigned after photos from a 2005 Halloween party showed him in blackface while dressed as a Hurricane Katrina victim.