Argentine President Cristina Fernandez de Kirchner has undergone surgery to treat bleeding on her brain, at a hospital in Buenos Aires.
The operation, which has lasted about two hours, "went very well" said her spokesman, Alfredo Scoccimarro.
Ms Fernandez, 60, is expected to remain in intensive care for the next 48 hours and stay in hospital until next week.
She was ordered to rest for at least a month after doctors discovered the subdural haematoma.
"The president is in good spirits and is already in her room," said Mr Scoccimarro.
The president's leave of absence means she will have to suspend campaigning for congressional elections.
The break from the campaign trail is considered awkward for the president as some opinion polls have suggested the government could lose control of Congress in the poll on 27 October.
While her party has done well in the primaries on a nationwide level it has failed to win a key seat in the province of Buenos Aires, where her rival and former cabinet chief Sergio Massa beat Ms Fernandez's candidate.
Medical experts say recovering from this type of surgery is a long process, and her lay-off is now likely to be longer than a month.
Vice-President Amado Boudou, who is facing a corruption investigation, will be in charge of the country during her leave.
The president's spokesman, Alfredo Scoccimarro, issued a statement on Sunday saying her doctors had carried out a brain scan in August after a previously undisclosed trauma thought to have been caused by a fall.
They found nothing untoward, but on Saturday, she went to hospital for checks for an irregular heartbeat and headaches, and a further scan revealed the subdural haematoma - bleeding between the brain and the skull.
The hospital treating her said on Monday she had experienced a slight loss of muscular strength in her left arm, and recommended surgery to drain the haematoma.
President Fernandez was first elected in 2007 and then returned to power by a comfortable majority in 2011.
Her health has been followed closely since the sudden death of her husband, former President Nestor Kirchner, from a heart attack in 2010.
She has been admitted to hospital on a number of occasions while serving as president. She has low blood pressure and had to have a thyroid gland removed in 2012.