Brazil's President Luiz Inácio Lula da Silva has been discharged from hospital after undergoing emergency surgery for a brain bleed, doctors said.

The 79-year-old appeared alongside his medical team at a news conference at Sírio-Libanês Hospital in São Paulo.

"This here is not an interview, this is simply a session to say thanks. To thank, firstly, God, who has looked after me in a very generous manner," he said.

Lula was taken to hospital on Monday after he had complained of a severe headache.

Doctors performed a craniotomy on the president, a procedure in which part of the bone is surgically removed from the skull to treat the bleeding and relieve the pressure. The bone is then replaced.

The brain bleed, or intracranial haemorrhage, was caused by a blow to the head he sustained when he fell in his bathroom at the presidential residence in October, according to a hospital statement.

"Thank you very much for the prayers," Lula added on Sunday. "And for those who only have hate, you're forgiven. I am here, alive, whole, and with more desire to work."

On Tuesday, doctors said the president was in a stable condition following the surgery and was conscious.

Lula was "lucid" and conversing with medical staff, they added.

They also insisted that he had not sustained any brain injury and was not experiencing after-effects from the surgery.

Asked when he would return to the capital, doctors had said that if everything went well, they expected Lula to be back in Brasilia "next week".

While Lula was in hospital, Vice-President Geraldo Alckmin took on some of the president's commitments.

The doctors said the bleeding was a result of the fall Lula had sustained in October.

They explained that it was not unusual for problems from a blow to the head to appear "months later".

Lula had slipped in the bathroom in the Alvorada Palace on 19 October and hit the back of his head. On Sunday, he explained he had been cutting his toenails at the time and had been sitting down.

He went on to have five stitches. On his doctors' advice, the president cancelled his planned trip to Russia for a summit of the Brics countries.

He returned to full duties days later.

Lula has been in power since January last year after narrowly beating the incumbent, Jair Bolsonaro, in a bitterly fought election.

During the election campaign, he often joked that he had "the energy of a 30-year-old".