Brazilian President Dilma Rousseff was checked over the weekend at a hospital in Sao Paulo by doctors, who found symptoms of pneumonia and ordered her to rest for a day, the president's personal physician said.

"She had flu during the week and had already scheduled her regular medical exam for next Friday, but in light of these symptoms we determined to do the checkup earlier. The pneumonia symptoms were detected during the examination," Dr. Roberto Kalil Filho told reporters Sunday.

The president, who according to the official agenda should have spent the weekend in Brasilia without taking part in the public celebrations for International Workers' Day, traveled Sunday to Sao Paulo and was immediately taken to the Sirio Libanes Hospital.

Rousseff suffered "from common flu symptoms almost as a routine, but the flu symptoms were getting worse to the point that the beginnings of pneumonia were detected," Kalil Filho said.

Rousseff had scheduled a series of medical examinations for Friday as part of the follow-up to cancer treatments that ended last year.

"The exams are all good, except for the diagnosis of pneumonia. But she is basically a healthy person," the doctor said.

Rousseff vaccinated herself last Monday against the flu while launching the national vaccination campaign, but Kalil Filho ruled out the possibility that her pneumonia was a reaction to the medication.

"It has no relation at all to the vaccine," the doctor said.

The president must rest for a day and will not have to return to the clinic for further exams, Kalil Filho said.

"She'll have to return tomorrow (Monday) to Brasilia and will perhaps get back to work with a certain calm during the week, on Tuesday or Wednesday. It depends a lot on her," the doctor said.