RICHMOND, Va. — Virginia Gov. Ralph Northam acknowledged Friday that he appears in a photo on his 1984 medical school yearbook page that shows a person in blackface and another wearing a Ku Klux Klan robe.

The revelation of the photograph prompted some Republicans to call for his resignation. Northam quickly apologized.

The Democratic governor confirmed in a statement that he was in the photo wearing a costume “that is clearly racist and offensive.” Northam did not say which costume he was wearing.

Gov. Ralph Northam prepares to address a news conference at the Capitol in Richmond, Va., on Thursday.

“This behavior is not in keeping with who I am today and the values I have fought for throughout my career in the military, in medicine, and in public service. But I want to be clear, I understand how this decision shakes Virginians’ faith in that commitment,” he said.

Republican state Sen. Bryce Reeves said in a statement that Northam should resign if the reports of the photos are accurate.

“I hope that this picture is inaccurate and that the governor brings clarity to this issue. This has no place in Virginia,” Reeves said.

Former Obama housing secretary Julian Castro, a Texas Democrat who has announced he will run for president in 2020, tweeted that Northam should resign.

“It doesn’t matter if he is a Republican or a Democrat. This behavior was racist and unconscionable,” he wrote.

If Northam were to resign, Lt. Gov. Justin Fairfax, who is African-American, would assume the governor’s office.

For now, Northam’s close allies haven’t said anything publicly. Democratic Sen. Jennifer McClellan, a well-known African-American lawmaker from Richmond, just shook her head when approached by a reporter seeking comment.

The Virginian-Pilot obtained a copy of the photo Friday from the library of Eastern Virginia Medical School, which Northam attended. The photo shows two people looking at the camera – one in blackface, the other in white Klan robes.