The interim head of Boston's Roman Catholic Church, Richard Lennon, has called for unity, at the end of a week which saw the resignation of archdiocese's most senior figure, Cardinal Bernard Law.

How many are broken-hearted, how many are captives of the crimes and the sins of sexual abuse against minors? Bishop Richard Lennon

Cardinal Law stepped down on Friday after repeated claims that he failed to take action against paedophile priests.

In Sunday Mass at the Cathedral of the Holy Cross on Sunday, Bishop Lennon received a standing ovation after speaking frankly of troubles that have beset America's fourth largest Roman Catholic archdiocese.

Outside the building, 50 protesters served as a reminder of the problems the bishop faces: an estimated 450 lawsuits from alleged victims of sexual abuse by clergy members, possible bankruptcy proceedings and a federal investigation into the abuse allegations.

Bishop Lennon will have full authority as archbishop until a permanent successor is appointed by the Vatican.

Quiet return

On Saturday, Cardinal Law, 71, returned to the US from Rome, where the Pope accepted his resignation.

Law says it is time to reflect

Cardinal Law, one of the most senior Roman Catholics in the US, had faced calls to step down from some of his own priests over the child sex abuse scandal.

Critics accused him of moving priests from one pulpit to another rather than confronting the problem of paedophile priests.

On his flight from Rome to Newark, New Jersey, he was asked by reporter from the Boston Globe newspaper what role he would play in the Church after stepping down.

We're looking for a new beginning Brian Flaherty, protester

"I honestly do not know," he replied. "I need to turn my thoughts and prayers toward figuring that out."

"I really think that what I have done is best for the Church and I have to leave it at that. I think it is best that I return quietly," he said.

He was reported to have returned to Boston on Sunday.

'Average Joe'

Bishop Lennon, 55, briefly greeted protesters outside the cathedral, one of whom held a placard reading "Law's gone, the fight goes on".

An estimated 450 lawsuits have been brought against the archdiocese

"I hope he's a good guy, but we have very low expectations of him. I think we're all very suspicious and we should continue to be. It's the naivete and docility of Catholics that led to this in the first place," Terry McKiernan told the Associated Press.

But some churchgoers expressed hope that the church could put the crisis behind it.

Brian Flaherty, who said he had attended a lesson taught by the Bishop Lennon, described him as "a down to earth, average Joe".

"He hasn't been tainted by the scandal. He's free from criticism, free from the scandal," Mr Flaherty said.

"We're looking for a new beginning."