(CNN) -- A Scottish cardinal who had earlier challenged allegations of sexual impropriety -- claims that once again shined an international spotlight on alleged sexual abuse involving Roman Catholic clergy -- reversed course Sunday and apologized.
"I wish to take this opportunity to admit that there have been times that my sexual conduct has fallen below the standards expected of me as a priest, archbishop and cardinal," Cardinal Keith O'Brien said in a statement.
Until days ago, O'Brien was the archbishop of St. Andrews and Edinburgh.
He has been dogged by allegations he abused four men studying to be priests in the 1980s.
"In recent days certain allegations which have been made against me have become public. Initially, their anonymous and non-specific nature led me to contest them," O'Brien said.
"To those I have offended, I apologize and ask forgiveness."
O'Brien, 74, also apologized to "the Catholic Church and people of Scotland."
He did not explain exactly what "conduct" he was referring to.
O'Brien told Pope Benedict XVI in November that he would resign effective his upcoming birthday, on March 17. But Benedict decided to make the resignation effective immediately in light of the pope's imminent resignation, the Scottish Catholic Media Office said.
According to his biography on his archdiocese's website, O'Brien asked to step down in light of his "approaching ... 75th birthday (and) health concerns."
Meanwhile, he had been thrust into the ongoing story about sexual abuse in the church after the British newspaper The Observer reported that three priests and one former priest, as long as 30 years ago, had accused O'Brien. The Observer did not recount the details of the claims or identify the men but said one of the priests alleged "the cardinal developed an inappropriate relationship with him."
The Scottish Catholic Media Office said then that O'Brien contested the claims and was "taking legal advice."
The same office released O'Brien's new statement on Sunday.
Born in Northern Ireland, O'Brien moved to Scotland as a child, graduating in 1959 from the University of Edinburgh. Ordained as a priest six years later at age 29, he later held various positions -- including as a math and science teacher, as well as rector and spiritual director -- at schools in Scotland, in addition to working as a priest.
He was named archbishop in 1985 and became a cardinal 18 years later.
Cardinal Roger Mahony of Los Angeles, meanwhile, is facing fresh attention over what role he may have played in the cover-up of sexual abuse by priests.
The Vatican has also been plagued by another scandal in recent days, as Benedict was ending his papacy.
Two Italian publications said Benedict, 85, resigned not because of his advanced age but because of a brewing scandal over the blackmail of gay priests by male prostitutes in Rome.
Benedict received a 300-page report in December detailing the possible blackmail, la Repubblica newspaper and the Panorama news weekly reported, citing an unidentified senior Vatican official and dozens of unnamed sources.
The Vatican emphatically denied the allegations, with Secretary of State Tarcisio Bertone criticizing a rash of "often unverified, unverifiable or completely false news stories" as the cardinals prepare for their conclave to select a new pope.
CNN's Matt Smith, Laura Smith-Spark, Greg Botelho and Hada Messia contributed to this report.