The former head of a major Greek bank has been arrested in Turkey, the latest in an expanding investigation into several Greek officials allegedly involved with issuing faulty loans.

Angelos Filippidis, the former chief executive officer of the now-defunct Hellenic Postbank, was arrested on Friday in Istanbul, Greek police confirmed.

Filippidis's lawyer told AFP news agency that the ex-CEO appeared before a Turkish magistrate on Saturday and asked to return to his country in order to face questioning.

At least 25 people have been arrested so far in Greece by the anti-corruption magistrate, which has been looking into a series of loans issued by Postbank between 2007-2012 and resulted in losses of more than 400 million euros.

An unsecured loan is particularly advantageous to the borrower since no guarantee or collateral is required.

Filippidis denied any wrongdoing earlier in the week.

"All the loans were issued with unanimous decisions by the board and all the procedures were respected," he told Skai Radio on Thursday. "If I could turn back time, I would issue them again today."

Major restructuring

Greek authorities have gotten tough on corruption, bringing to light the extent of fraud before the country’s economy collapsed in 2010.

Greek Finance Minister Yannis Stournaras backed Anastasia Sakellariou, head of the country's bank bailout fund, the Hellenic Financial Stability Fund (HFSF), after she was also charged in connection to the fraud allegations on Friday.

"I fully trust and respect Greece's justice system, but I also fully trust Mrs Sakellariou, her integrity, her professional expertise and above all, her work so far," Stournaras said.

Sakellariou was charged with breach of trust, court officials said.

The HFSF was set up in 2010 to restructure the debt of Greece's four biggest banks. The fund pumped about 4.5 billion euros into Hellenic Postbank, before the bank's healthy assets were absorbed by Greece's Eurobank.

The Greek banking sector also underwent major restructuring last year under the terms of the country's bailout deal with the European Union and International Monetary Fund.

Source: Agencies