At around 12.30pm, the yield on bonds traded in the secondary market was 4.014%, up around 0.1 of a percentage point from the same time on Wednesday.

Bond markets across Europe are under pressure after the recent news that euro-zone consumer inflation had jumped to a three-year high, prompting expectations that the European Central Bank may raise interest rates in the coming months. The preliminary figure for December inflation is 1.1%, up from 0.6% in November.

Portuguese bond yields last year reached record lows, just four years after the country was forced to seek a euro-zone bailout because of its high level of indebtedness. Portugal public debt has continued to rise, but its financing costs have fallen sharply thanks to lower yields.