It sold 60 million euros of 18-month bills at a yield of minus 0.51pc, having paid minus 0.37pc at the last such auction in April.
It also sold 12 million euros of three-month bills at a yield of minus 0.43pc versus minus 0.4pc in September.
Total bids amounted to 409 million euros. No further T-bill auctions are planned this year.
Analysts said negative yields reflect the expansive monetary policy of the European Central Bank, adding they could remain negative well into 2020.