Portugal's borrowing costs increased to the highest since November as the government sold €750m of 18-month bills.

The securities due in March 2015 were issued at an average yield of 2.293%, the country's debt management agency said.

That compares with an rate of 1.603% at a previous auction of 18-month bills in June and is the highest since November 21, when it sold the securities at a yield of 2.99%.

Today's auction attracted bids for two times the amount offered, compared with a bid-to-cover ratio of 2.1 in June.

Portugal's 10-year yield breached 8% for the first time in eight months on July 3 when a rift in the ruling coalition emerged.

Portuguese Prime Minister Pedro Passos Coelho later that month pushed ahead with a government reshuffle and pledged to complete a bailout programme that includes new spending cuts.

The country sold 10-year debt in May for the first time in more than two years as it seeks to regain full access to debt markets after requesting the bailout from the European Union and the International Monetary Fund in 2011 following a surge in debt levels and borrowing costs. The country pays 3.2% on its bailout loans.

The debt agency today also sold €500m of three month bills due in December 2013 at an average yield of 1.081%, attracting bids for 1.8 times the amount offered. That compares with an average yield of 0.766% at a previous auction of three-month bills on August 21, with a bid-to-cover ratio of 3.4.