Greek small-scale private investors protested against the sovereign debt restructuring plan in central Athens on Tuesday, requesting the government's support for their losses.

Dozens of holders of Greek state bonds who lose up to 75 percent of their investment under the debt swap scheme demonstrated outside the parliament and the Finance Ministry building, holding banners with slogans such as "Shame. Return our money."

The demonstrators represented some 15,000 small-scale private investors who held Greek state bonds that were subjected to a 53.5 percent nominal "haircut" this spring under the so-called voluntary Private Sector Involvement (PSI) agreement Greece reached with private creditors as part of efforts to address an alarming debt crisis.

After a formal invitation to holders of bonds issued under Greek and foreign laws, the debt-laden country secured a high participation rate that paved the way for the restructuring of some 200 billion euros out of an over 360 billion euros debt burden.

Under the plan which is due to be completed by late April, old bonds are exchanged with new ones of longer maturities and reduced face value of the debt swapped.

Small-scale investors request an exemption from the PSI or significant support, arguing that they cannot cope with the losses as big banks. Pensioners who have invested a life's savings on Greek bonds, and depended on their investment to counter the austerity, all of a sudden lose a great part of their money.

Government officials said that the haircut is a necessary step to overcome the debt crisis, but two Greek small-scale investors have already filed a first appeal with the country's highest administrative court for the annulment of the cabinet's decree implementing the debt write down plan.

The PSI plan opened the way for the release of a vital multi-billion euro rescue loans package to Greece from the European Union and the International Monetary Fund this spring, the second in two years, in order to avoid a financial meltdown that could destabilize the entire euro zone.

Since 2010 Greece has been relying on international rescue loans to stay afloat in exchange of a painful austerity and reform program to resolve the debt crisis.