Tensions on European government debt markets increased overnight as investors digested the results of a first-round French presidential vote, a Dutch political crisis and worries over Spanish debt.
In Spain, worries about the government's ability to reach debt-reduction targets have resurfaced. The yield on 10-year Spanish bonds climbed to 5.9%.
Markets see 6% as the point at which a bail-out will need to be sought.
Meanwhile, the Netherlands risks loosing its triple A credit rating after the collapse of talks on austerity measures.
Bond analysts say markets are increasingly worried about the idea of a renegotiation of European treaties.