In a message on his Twitter account Tuesday, Pope Francis deplored graft, calling it "a cancer on society".
"Corruption is a cancer on society," read the brief Tweet on his @Pontifex account, which has over 22 million followers.
The message came on the day that five officials from Rome city council including the former head of the municipal garbage collection service went on trial for graft.
The trial is the first to follow a major corruption probe that uncovered an alleged mafia network accused of rigging tenders and siphoning off millions of euros.
The probe led to scores of arrests and implicated businessmen and politicians including Rome's former conservative mayor Gianni Alemanno.
Italian politicians of all stripes have been hit by a slew of corruption scandals in recent years, while the leak of private papal letters by Benedict XVI's butler in 2012 revealed serious graft allegations in the Vatican government.
Francis has blasted graft in several homilies, including one on 25 May in which he warned that wealth that is not shared breeds corruption.