Brazilian President Luiz Inacio Lula da Silva said, on Thursday, that the rioters likely had inside help.

Lula told journalists he had ordered a "thorough review" of presidential palace staff after Sunday's violent riots, which saw supporters of his far-right predecessor Jair Bolsonaro storm the presidential palace, Congress, and Supreme Court and cause widespread damage.

"I am convinced that the door of the Planalto (presidential) palace was opened for people to enter because there are no broken doors," the President said in Brasilia.

"This means that someone facilitated their entry," he added.

Elsewhere in his remarks, he affirmed that "we will investigate calmly to see what really happened." 

The big picture

Riots in Brazil that sowed destruction across several government buildings in Brasilia by followers of former leader Jair Bolsonaro lasted for approximately three hours on January 8 before Brazilian security forces were able to disperse rioters and take control of Parliament.

Brazilian security forces cleared riot camps Monday and arrested 1,500 people as President Luiz Inacio Lula da Silva condemned "acts of terrorism" after far-right supporters of former President Jair Bolsonaro broke into the country's Planalto presidential palace, Congress, and Supreme court building on Sunday.

A federal security intervention was announced by Brazilian President Luiz Inacio Lula da Silva until January 31 after the capital was secured.

Bolsonaro had been defeated by leftist President Luiz Inacio Lula da Silva in the latest election. Lula da Silva was inaugurated on January 1. However, Bolsonaro supporters defied the democratic process and stormed government buildings, including parliament, where they called for "military intervention". This incident came after Bolsonaro made baseless accusations of possible election fraud that could be paralleled to that of former US President Donald Trump.

On his part, Bolsonaro tweeted that he had been hospitalized in Florida with abdominal pains stemming from a near-fatal knife attack when he was campaigning for the presidency in 2018. 

Bolsonaro has alleged that he is the victim of a conspiracy against him by Brazil's courts and electoral authorities.

The ex-President traveled to Orlando on the second-to-last day of his term -- snubbing Lula's inauguration, in a break with tradition.

Bolsonaro, 67, took to Twitter Sunday night to condemn the "pillaging" in Brasilia but rejected Lula's accusations that he incited the attacks and defended the right to what he called "peaceful protests".