A banker who allegedly used the Vatican Bank and other aspects of Holy See finances to manipulate the market for his bank stock price continues to be under investigation, as Italian authorities froze millions of euros in his personal assets on Tuesday.

Giampietro Nattino, the head of Banca Finnat Euramerica SpA, allegedly used Vatican financial institutions as cover for "a complex stock operation which resulted in criminal behavior regarding market manipulation." Police said he used "misleading and false" methods to "substantially alter" the price of shares in his bank, Reuters reports.

The alleged manipulation used the Institute for Religious Works, known informally as the Vatican Bank, and APSA, which oversees Vatican real estate and investments. Vatican investigators suspect that during a stock placement handled by Nattino's bank, shares were bought through the accounts at APSA before the shares were allocated to other investors.

Nattino is also accused of providing false information to Italy's stock regulator, Consob.    

Italian magistrates are investigating two people who were managers at APSA in 2011, suspecting they were collaborators with Nattino's bank.

In a statement, Nattino said that his work had "always been characterized by maximum transparency and correctness." He said the frozen assets belong to him, not his bank, and he pledged cooperation with investigators.

Efforts to reform Vatican finances have been ongoing. Vatican officials have closed many outside accounts in an effort to block corruption.

In June 2013, a longtime accountant at APSA, Monsignor Nunzio Scarano, was arrested and faced charges of conspiracy to smuggle 20 million euros from Switzerland to help friends avoid taxes.

Though he was acquitted on those charges, and denies all charges of wrongdoing, he will face a separate trial for alleged money laundering.