LONDON — The Vatican is looking into allegations of "inappropriate behavior" by Cardinal Keith O'Brien, Britain's most senior Catholic cleric, officials said Sunday. The claims came at a sensitive time, as O'Brien and other cardinals prepare for a conclave to choose the next pope.

O'Brien, who heads the Roman Catholic Church in Scotland, was taking advice from lawyers after British newspaper The Observer reported that three priests and a former priest have filed complaints to the Vatican alleging that the cardinal approached them in an inappropriate manner.

The paper did not cite the names of the priests, but it said their allegations date back to the 1980s.

"Cardinal O'Brien contests these claims and is taking legal advice," Peter Kearney, a spokesman for the Scottish Catholic Church, said. He declined to comment further.

A Vatican spokesman, the Rev. Federico Lombardi, said the complaints had been channeled through the office of the papal nuncio — the Vatican's ambassador — in London. "The pope has been informed, and the question is in his hands," Lombardi said.

In the coming weeks, O'Brien, 74, is expected to join a conclave of cardinals at the Vatican to elect the next pontiff, following the resignation of Pope Benedict XVI. Benedict announced earlier this month that he will step down on Thursday — the first pope to resign in some 600 years.

In comments to the BBC on Friday, O'Brien said the next pope would be free to consider changing church policy on issues that were not "basic dogmatic beliefs."

He said he believed that the requirement for priestly celibacy is not "of divine origin" and could be reconsidered.