MINNEAPOLIS — St. Paul-Minneapolis Archbishop John Nienstedt announced Tuesday that he’s stepping down from public ministry while police investigate an allegation that he improperly touched a boy during a public photo session four years ago, an accusation he strongly denies.

The announcement is the latest blow to an archdiocese that has faced intense scrutiny since a former employee went public with claims that church leaders mishandled sexual abuse allegations.

In a letter posted on the archdiocese’s website, Nienstedt said he is accused of touching the boy on the buttocks during a photo session following a confirmation ceremony in 2009. Confirmation is a Roman Catholic sacrament during which people confirm their faith. The church considers people who have gone through the process to be responsible for their own spiritual growth.

Nienstedt said he learned of the accusation over the weekend and doesn’t know who is making the claim.

“I presume he is sincere in believing what he claims, but I must say that this allegation is absolutely and entirely false,” Nienstedt wrote. “I have never once engaged in any inappropriate contact with a minor.”

Nienstedt had already been facing public calls for his resignation. In recent months, police have launched investigations into several abuse claims and Nienstedt’s top deputy stepped down.