Vatican spokesman Federico Lombardi said he was "confident the situation will be clarified quickly and in full to eliminate any shadows hanging" over Cardinal Crescenzio Sepe and Church institutions.
Sepe, "as he has already indicated, will fully collaborate" after the investigation was launched Saturday, Lombardi said in a statement, also underlining his "respect and solidarity" for the cardinal.
Lombardi said the archbishop had been an "intense and generous" worker for the Church.
Lombardi also pointed out that Sepe held a passport from the Vatican City which gave him diplomatic immunity, which had to be taken into account for legal proceedings in Italy.
The prosecution in Perugia, central Italy, is investigating allegations that Sepe accepted kickbacks when in 2001-2006 he was head of the body which manages funds for the Catholic Church's missionary work and also the Vatican's vast real estate holdings, especially in Rome.
Sepe allegedly sold a building at a favourable price to Italy's then infrastructure minister, Pietro Lunardi.
The building was then renovated by the Rome construction magnate Diego Anemome, who is under investigation by prosecutors over several public tenders, including infrastructure for the Group of Eight summit in Italy last year.
SIC: TomCom