Two more senior Brazilian officials have resigned in the latest blow to the government of President Dilma Rousseff, BBC News reports.

They are Sports Minister George Hilton and Col Adilson Moreira, who was organising security at the Olympic Games in Rio de Janeiro next August.

Col Moreira reportedly wrote that he was ashamed the country was being led by "an unscrupulous group".

The resignations come as Rousseff battles for her government's survival in an impeachment process.

Col Moreira led the National Force for Public Security, whose members will guard sporting venues during the Olympics.

Brazilian media reported he had sent an email to his colleagues criticising President Rousseff and other senior officials.

Brazilian officials said the planning for the Olympic Games would not be affected by Col Moreira's and Hilton's resignations.

Supporters of the president marched on Thursday evening in a number of Brazilian cities to show their opposition to the impeachment proceedings.