President Cristina Fernandez must rest for a month due to a subdural hematoma on her brain, just three weeks before Argentina's legislative elections, doctors said.

The condition was diagnosed Saturday by the doctors attending the president in a Buenos Aires hospital.

Fernandez is suffering from a "chronic subdural collection" of blood under the membrane that encloses the brain, and the condition will force her to suspend her regular activities for 30 days, the Office of the President said in a statement.

Fernandez underwent a medical exam at the Fundacion Favaloro health center, where she was admitted for eight hours on Saturday.

The 60-year-old Fernandez suffered trauma to the brain in August and underwent a CAT scan, which doctors pronounced "normal," and she has had no complications from that incident up to now, the Office of the President said.

The president went to the hospital for "a cardiovascular test for an arrhythmia ... and because she complained of a headache, a neurological evaluation was made at the (foundation's) Neurosciences Institute," presidential spokesman Alfredo Scoccimarro said.

After the exam, Fernandez, accompanied by her daughter Florencia, went to her official Olivos residence on the northern outskirts of Buenos Aires.

Fernandez has kept up an intense public schedule in recent weeks and has been an important presence in the election campaign trying to pare down the lead of greater than 10 percentage points that voter surveys give to her political adversaries in the run-up to the legislative balloting.

Fernandez in October 2010 lost her husband and predecessor, Nestor Kirchner, who died at the family residence in Santa Cruz province from a massive heart attack. EFE