Pope Benedict XVI on Tuesday accepted the resignation of the Archbishop of Philadelphia, Cardinal Justin Rigali, who was caught up in a long-running paedophile priest scandal in the archdiocese.

Rigali, 76, had submitted his resignation last year because of his age, the Vatican said in a brief bulletin, without mentioning the sex abuse scandal.

All archbishops are required by church law to offer their notice to the pontiff on their 75th birthday. They must then await the decision of the pope.

The Archbishop of Denver, Charles Chaput, will take over the role, the bulletin said.

In 2005, a grand jury report had found that Rigali had covered up complaints of abuse allegedly carried out by dozens of Philadelphia priests, and had kept them in active service despite the charges against them.

Rigali suspended 21 suspected paedophile priests in March this year, and expressed his "sorrow for the sexual abuse of minors committed by members of the Church, and above all, the clergy."

The archdiocese issued a statement saying that it had "made significant progress in protecting children and in enquiries into the alleged abuse and allegations of violence."

"The suspensions are not convictions or final verdicts, but provisional measures taken while the enquiry is carried out," it said.

The Church has come under intense pressure in recent years over the scandal of child-abuser priests, which peaked last year with a string of high-profile revelations in the US, Belgium, Germany and Ireland and Austria.

The Holy See has been accused of being slow to react to thousands of complaints and of protecting abusers. Amnesty International said in April that it was still failing to meet international obligations to protect children.

Just three weeks ago, the pontiff accepted the resignation of Californian bishop Daniel Walsh, accused of allowing an alleged paedophile priest from his diocese to flee to Mexico.

Father Xavier Ochoa had admitted to the bishop in April 2006 that he had abused young boys but the police were only told three days later by a diocesan lawyer. By that time, Ochoa had fled to Mexico where he is still at large.

Benedict called last year for a zero tolerance approach to child abuse by clergymen and asked bishops to work together with local law enforcement.

National bishops conferences around the world are set to come up with common guidelines against paedophiles by May 2012.

The Vatican also announced this month that it is turning to the Internet in its struggle against child abuse with a new website allowing clergy around the world to share information on eradicating the problem.

But many in the Church are concerned that the cases uncovered so far may only be the tip of the iceberg since abuses in much of the developing world -- including in Africa and Latin America -- have so far received little attention.