Brazilian presidential candidate among dead after plane crash

Brazilian presidential candidate Eduardo Campos, a contender to unseat President Dilma Rousseff in October elections, is among seven people who died when his jet crashed in the city of Santos.

Rescuers work on the site of the crash of the Cessna 560XL aircraft carrying the presidential candidate of the Brazilian Socialist Party (PSB) Eduardo Campos (AAP)

Campos, a 49-year-old socialist who had been running third in the polls, was flying to Sao Paulo to record a TV segment when his Cessna 560XL slammed into a gymnasium and several houses, breaking into pieces and igniting a large fire.

Rousseff declared a state of national mourning and suspended her campaign for three days.

"All of Brazil is in mourning. We lost a great Brazilian today, Eduardo Campos. We lost a great comrade," the president said in a statement.

Campos's plane was en route from Rio de Janeiro's Santos Dumont airport to Guaruja airport outside Sao Paulo when it hit bad weather, according to air force spokesman Pedro Luis Farcic.

"As it was preparing to land, the plane fell due to bad weather. Air traffic control then lost contact with the aircraft," he said.

All seven people aboard the plane died, the air force told media network Globo.

The other passengers were advisers, a photographer and a videographer.

An AFP photographer said pieces of the destroyed jet were strewn around the crash site in a bustling residential neighbourhood of Santos, a port on the Atlantic.

Flaming piles of rubble sent up a large column of smoke, and several houses were on fire.

Santos firefighters said at least 10 people were injured, according to Globo's online news portal G1.

The air force said it had launched an investigation into what caused the medium-sized jet to crash.

Campos, a former governor of the northeastern state of Pernambuco, had eight per cent support from likely voters, according to a survey released on July 22 by polling firm Ibope ahead of the October 5 first-round election.

Rousseff, who is standing for a second four-year term, leads the race with 38-per cent support, while social democrat Aecio Neves has 22 per cent, the poll found.

Campos, who was married with five children, had been running on a platform of change after 20 years of government by Rousseff's Workers' Party (PT) and Neves's PSDB.

He had served as science and technology minister from 2004 to 2005 under Rousseff's mentor and predecessor Luiz Inacio Lula da Silva.