Loquacious US cardinals have been told to stop talking to the media after a series of press briefings that delighted journalists, but broke with tight-lipped Vatican tradition.

This week, as the college of cardinals entered its period of "general congregations" designed to prepare it for the election of a new pope, press conferences held at the Pontifical North American College had proved a popular way of providing information during what is usually a secretive process.

However, the ensuing reports were apparently enough to provoke ire in some quarters. "Concern was expressed in the general congregation about leaks of confidential proceedings reported in Italian newspapers," said Sister Mary Ann Walsh, the US cardinals' spokeswoman, in a statement. "As a precaution, the cardinals have agreed not to do interviews."

The Vatican said it had not put pressure on the Americans to stay quiet. But a Vatican spokesman said that cardinals had perhaps decided among themselves to cancel the briefing as they increasingly appreciated "the importance of keeping things among themselves".

153 cardinals participated in the fourth general congregation on Wednesday morning, with 113 of them cardinal electors who will take part in the conclave to choose a successor to the emeritus pope Benedict XVI. Another elector was due to arrive later on Wednesday, meaning that by Thursday there will be just one missing. A date is expected soon after his arrival, but there is increasing speculation that it may not start early next week as had been expected. The church has until 20 March to start the conclave.

In its official communications, the Vatican says it cannot be specific about what the cardinals are discussing in their meetings and can only give a general subject area. Most cardinals have remained near-silent during the process, but some of the Americans, while under an oath of confidentiality, had spoken rather more freely, giving insights into how the meetings were progressing while not giving away any great secrets.

However, comments reported in the Italian daily newspaper La Stampa were apparently viewed as overstepping the mark and violating their oath. It was unclear specifically which remarks were concerned.

Cardinal Sean O'Malley, archbishop of Boston, was quoted as saying there were "two schools of thought" in the college of cardinals: those who felt the Roman curia would be best reformed by someone within it, and those who believed an outsider was needed. Francis George, archbishop of Chicago, was quoted as saying the cardinals wanted to be briefed on the Vatileaks scandal in order to make the right choice.

Meanwhile, in the first photograph to emerge from his time at Castel Gandolfo, the emeritus pope was shown strolling through the gardens with his trusted secretary George Gänswein. Dressed head-to-toe in white, Benedict appeared to be wearing a floor-length cassock with a jacket and baseball cap, and was walking with a cane.

The picture was published by the celebrity magazine Chi, which last month published photographs of a pregnant Duchess of Cambridge on holiday. Chi also featured a picture of Cardinal Roger Mahony, under fire for having shielded priests accused of abuse, sipping wine in a Roman restaurant.

The clerical abuse scandal – which has overshadowed the papal transition period – continued to do so on Wednesday, as a group representing abuse survivors released a so-called "dirty dozen" list of the papabili it would least like to be made the head of the Roman Catholic church.

Highlighting what it said were failures to properly handle abuse claims, Snap – the Survivors' Network of those Abused by Priests – said its list was based largely on legal documents, witness statements and media cuttings.