The Argentinian president, Cristina Kirchner, is to be operated on in January for thyroid cancer, according to a spokesman.

Spokesman Alfredo Scoccimarro said the cancer was discovered on 22 December, and follow-up tests showed that it has not spread to her lymph nodes, nor has it metastasized.

He said Fernandez will undergo surgery on 4 January and then take 20 days of medical leave, during which the vice-president, Amado Boudou, will run the country.

The operation on the president will take place at Buenos Aires' Austral hospital.

Kirchner, 58, who went from being a senator during the presidency of her husband, Néstor, to becoming the first elected female president of Argentina in 2007, was re-elected in October with one of the widest victory margins in her country's history.

A president from 2003 to 2007, he had been a contender to succeed her but died from a heart attack in October last year at the age of 60.

During this year's elections, which she won on the back of strong economic growth, Fernandez secured nearly 54% of vote, with her closest challenger, the socialist candidate Hermes Binner, on just 17%.

Earlier this year, she accused the media of spreading rumours about her health, saying: "They will print anything every time my blood pressure drops."

Her comments came after reports in October that she was forced to cancel scheduled activities for a third time this year because of low blood pressure.