SAO PAULO (Reuters) - Brazilian presidential candidate Eduardo Campos was killed in a plane crash on Wednesday, local television channel GloboNews reported, throwing the country's October election into disarray and knocking local financial markets lower.

Campos' private jet crashed in bad weather in the coastal city of Santos, just south of Sao Paulo, as it was preparing to land. Television images showed smoke billowing from the crash site in a residential area.

GloboNews said Campos, the Brazilian Socialist Party (PSB) leader who was running third in opinion polls, died in the crash, without citing a source. A source in the PSB confirmed Campos was on the plane, but Reuters was not able to immediately confirm his death.

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Five people were rushed to a local hospital from the crash site, but a hospital official could not provide any names or information on their condition. GloboNews said seven people were on board the plane.

Campos, 49, had the support of about 10 percent of voters in recent polls. His death, if confirmed, will likely lead the two other leading candidates, President Dilma Rousseff and Senator Aecio Neves, to pause their presidential campaigns for a period of mourning just as the run-up to the Oct. 5 election was starting to capture the public's full attention.

Rousseff is leading in polls with about 36 percent of voter support. Neves has enjoyed about 20 percent support and was widely expected to face Rousseff in a second-round runoff.

Campos, a former governor of northeastern Pernambuco state, was running as a business-friendly leftist and had strong support from many banks and industrial groups. His death could see Marina Silva, his running mate, become the Brazilian Socialist Party's candidate.

Silva was not aboard the plane that crashed, the PSB source told Reuters. She placed a strong third in the 2010 presidential election and enjoys robust support from young voters and evangelical voters, but her pro-environment agenda means that many in Brazil's powerful agribusiness sector distrust her.

Brazil's main stock index lost as much as 2 percent following initial reports that Campos was on the crashed plane, but later pared losses to just over 1 percent. The currency also lost ground.

A police official in Santos said there were "certainly" fatalities in the crash, but could not say how many or provide any additional information.