The Vatican also plans to use signal jamming during the conclave to prevent electronic surveillance or communication outside the conclave, with the Vatican gendarmes overseeing the security measures. The provisions for the oath-taking are laid down in Vatican law.

Workers and clerics assisting the dozens of Catholic cardinals set to gather Wednesday to begin voting on the next pope had to swear to never reveal anything about the proceedings or else risk the Church’s gravest punishment: religious banishment. The employees took their oaths in the Papal Chapel.

Support staff for the cardinals who will elect Pope Francis' successor are taking an oath of secrecy on Monday before the conclave starts on Wednesday.

All of the 133 cardinals expected to take part in the secret conclave to elect a new pope have arrived in Rome, the Vatican said on Monday, with the race to succeed Pope Francis seen as wide open.

As a fireworks expert tests the Vatican's contemporary system for "holy smoke," Catholic cardinals mull their divergent priorities for Pope Francis' successor.