Explosions near Brazil's Supreme Court and Congress killed one person and prompted justices and staff to evacuate.
Two blasts rocked the capital Brasilia on Wednesday night just days before leaders of G20 countries were expected to meet in Rio de Janeiro, followed by a state visit by Chinese president Xi Jinping.
The first explosion took place in a parking lot near the court building, while another blast was heard in front of the court about 20 seconds later. A man was found lying on the ground outside the court.
Preliminary information suggested that the man, who has not been identified yet, set off the explosives after trying to enter the court, federal district vice governor Celina Leao said.
Ms Leao hoped the explosions were a "lone wolf" attack but said she could not be sure. “We are considering it as a suicide because there was only one victim. But investigations will show if that was indeed the case.”
Police deployed a bomb squad with an explosive disposal robot to sweep and investigate the blast. Police have not yet established a motive behind the attack.
The court's justices and staff had just ended a plenary session when the blasts happened at about 7.30pm. They safely exited the building, the authorities said.
“At the end of the [Supreme Court] session on Wednesday, two loud bangs were heard, and the ministers were safely removed from the building,” the court said.
Shortly after, all access to the area housing the court and the Congress were blocked.
Jose Chrispiniano, a spokesperson for president Luiz Inacio Lula da Silva, said the 79-year-old leader was not in the neighbouring presidential palace during the blast.
Attorney General Jorge Messias said the federal police would “investigate the explosions in the perimeter of the Three Powers Plaza with rigor and urgency".
The explosions took place around the Plaza of the Three Powers, the iconic square in the capital connecting the three branches of federal government, which was the site of last year's 8 January riots when supporters of former president Jair Bolsonaro stormed the buildings.
“I strongly condemn the attacks against the Supreme Federal Court and the House of Representatives. I express my solidarity with the ministers and parliamentarians,” the attorney general said on X on Wednesday.
“We need to understand the motivation behind these attacks, as well as to restore peace and security as quickly as possible.”
