Greece's short-term borrowing costs eased slightly in a treasury bill auction Tuesday, but the debt-wracked country still had to lure investors with a 4.54 percent return for paper maturing in six months' time.

The debt management agency said the auction raised (EURO)1.14 billion ($1.43 billion). The previous sale of six-month treasury bills brought in (EURO)812.5 million ($1.02 billion) offering a 4.68 percent interest rate.

By comparison, investors are prepared to incur a slight loss to get their hands on German six-month bills, which are seen as a safe haven during troubled times.

Since 2010, Greece has been unable to finance its government overspending through the usual path of selling bonds, which were demoted to non-investment grade after it emerged that the country's deficit was much higher than previously admitted.

Instead, Athens relies on international rescue loans, granted on condition it implements harsh austerity measures to tame the deficit and reform an economy already in its fifth year of recession.

But bailout payments were delayed by political instability and lagging reforms, forcing the country to rely ever more on treasury-bill sales _ initially designed to allow it some form of market access.

Last month, Greece sold (EURO)5 billion ($6.3 billion) worth of three-month debt to pay off a maturing bond held by the European Central Bank. The treasury bills are mostly bought by cash-needy domestic banks that use them as collateral to tap emergency European funds.

To qualify for the next, (EURO)31 billion ($38.9 billion) rescue loan installment, the conservative-led governing coalition must work out a new (EURO)11.5 billion ($14.5 billion) austerity package for 2013-14 that has to be approved by bailout creditors later this month.

The prospect of new pain after two-and-a-half years of income cuts and tax hikes has angered unions _ including police, judges and university teaching staff _ who are planning a series of protests or strikes in the next few days.

On Tuesday, about 200 pensioners from a Communist-backed union pushed their way into the Health Ministry during an Athens rally against healthcare cuts. The protest ended peacefully.

Private doctors and pharmacists this week refused to keep extending credit to Greece's largest state-run healthcare provider, EOPYY, noting the government has not paid them for months.