“I strongly condemn the attacks on the Supreme Court and the lower house,” he said in a statement published in X.
“We must know the motivation behind the attacks and restore peace and security as soon as possible.”
Pictures released by news agencies showed the dead man lying outside the court while officers cordoned off the area.
Earlier, the Supreme Court said in a statement that the building was evacuated as a “precautionary measure” after the blasts were heard.
The building is located across the square from the presidential palace. Local media reported that President Luiz Inácio Lula da Silva had left the area shortly before the explosions.