RIO DE JANEIRO (Reuters) - Confirmed coronavirus cases in Brazil surged past 600 on Thursday, more than doubling in two days, as a diplomatic spat over the disease’s origins between President Jair Bolsonaro’s son and the Chinese ambassador threatened relations with Brazil’s top trading partner.

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The president sidestepped this and other controversies in his weekly Facebook broadcast on Thursday evening, saying that the coronavirus outbreak in Brazil should peak in three to four months, and the country will return to normal in six to seven months.

But as Rio de Janeiro recorded its first fatalities and Latin America’s largest nation closed more land borders to visitors, the fallout from the president’s son’s late-night tweet on Wednesday snowballed.

After blaming the global spread of the virus on China, the son, Eduardo Bolsonaro, attempted to defuse the situation on Thursday, saying he stood by his criticism of the government in Beijing but did not intend to offend the Chinese people.

Foreign Minister Ernesto Araujo also hit back at Chinese Ambassador Yang Wanming’s initial response, which included a since-deleted retweet of a post describing the Bolsonaro family as a “huge poison” and a suggestion that Eduardo Bolsonaro had contracted a “mental virus” on a recent trip to the United States.

“It is unacceptable that the Chinese ambassador endorses or shares offensive posts aimed at the Brazilian head of state,” Araujo said in a statement, adding that he expected a retraction.

The Chinese Embassy responded by firing off a series of tweets to Eduardo Bolsonaro saying his words were “absurd, prejudiced ... (and) irresponsible” and that he should seek to educate himself.

Earlier, the Rio state government said a 63-year-old diabetic woman in the hilly interior of Rio de Janeiro state and a 69-year-old man, also diabetic, in the city of Niteroi, had both died from the virus.

The state of Sao Paulo reported the death of a 77-year-old man, bringing the country’s toll to seven. Earlier, the Health Ministry said the number of confirmed cases had risen to 621, an increase of 193 from Wednesday.

President Bolsonaro, who has faced criticism for his lax handling of an outbreak he initially called a “fantasy,” issued a decree restricting entry of foreign visitors at land borders with Argentina, Paraguay, Bolivia, Peru, Colombia, Suriname, Guyana and French Guiana. On Wednesday, Brazil began turning away Venezuelans at the border.

Responding to the deaths in Rio, state Governor Wilson Witzel urged people to stay indoors and to avoid gyms and beaches.

The country’s major cities have moved to restrict social gatherings in an attempt to slow the outbreak, with shopping malls and nightclubs asked to close. But the measures remain inconsistent between cities and states.

The rapid spread of the virus represents a major threat for the far-right populist Bolsonaro, who was already struggling to resuscitate the country’s weak economy.

On Wednesday night, Brazil erupted to the sound of banging pots and pans and shouts of “Bolsonaro out!” with housebound protesters expressing their anger toward the president for a second night in a row.