Silas Rondeau has denied any wrongdoing

Silas Rondeau is the latest public figure in Brazil to come under the spotlight as part of a wide-ranging investigation into corruption.

Senator Roseana Sarney said that Mr Rondeau believed it was "the correct thing to do".

Mr Rondeau, who denies any wrongdoing, is the most prominent figure yet to be connected to the scandal.

The move comes shortly after he held talks about the affair with President Luis Inacio Lula da Silva.

This is the first ministerial resignation since President Lula was re-elected last year, although scandals in his first term cost two key ministers their jobs.

'No proof'

Last week, police arrested almost 50 people, including a senior aide to Mr Rondeau, on suspicion of taking money from government contracts.

Brazilian media reported on Monday that police suspected the minister may have received a payment of over $50,000 (�25,000) from a company that won a contract to provide electricity to rural areas across the country.

Surveillance video aired on national TV showed an employee of the company delivering a package which police believe contained money to one of Mr Rondeau's key ministerial aides.

In his letter of resignation, the minister said he wanted to reaffirm his complete and absolute innocence and he complained about cruel lies and insinuations that had wounded his honour.

The country's justice minister said there was no proof to directly implicate his ministerial colleague.

The police investigation, called "Operation Navalha" - or Straight Razor - has focused on claims of fraud involving public works, including the building of bridges in isolated areas that were never completed.

An ex-governor, several mayors and ex-mayors, as well as several high-level state and federal employees, are among those who have been arrested as part of the investigation.

This latest controversy has been all the more embarrassing, says the BBC's Gary Duffy in Sao Paulo, as major infrastructure projects are central to the government's development plans for Brazil.

A substantial part of those proposals relate to energy and a whiff of corruption will not make it easier to win political support, our correspondent says.

This is also the latest in a long line of scandals spread across a number of parties that have undermined public trust in politicians in Brazil.