The cost of servicing Irish debt has hit a new record, despite data showing the first fall in unemployment since February.
The interest rate on Irish government debt has reached a high of 6.791%.
The rise comes as concerns about the country's economic health continue to nag at investors.
Latest official figures show a slight improvement in the unemployment rate, which fell back slightly for the first time since February.
However, the BBC reports investors are focused on forthcoming news about the stricken Anglo Irish Bank, which has been nationalised and needs another large injection of government money.
Estimates of the final bill for winding down the bank are as high as 35 billion euros ($US47.4 billion) - more than 20% of Ireland's gross domestic product.
Details are expected to be given by the government on Thursday.
However, the Irish Central Statistics Office said the standardised unemployment rate was 13.7% in September, down from 13.8% in August.
But the BBC reports the rate is still higher than the 13.2% average for the second quarter of the year.