He has called George W Bush the devil and described Barack Obama as a clown.

But Hugo Chávez's customary jabs at his neighbours to the north took an unusual turn this week, when the Venezuelan president suggested that Washington might be behind a wave of cancer among Latin American heads of state.

"Would it be so strange that they've invented the technology to spread cancer and we won't know about it for 50 years?" Chávez pondered, one day after Argentina's president Cristina Fernández de Kirchnerannounced she had been diagnosed with thyroid cancer and would undergo surgery in January.

Speaking on Wednesday during an end-of-year address to the armed forces, Chávez hinted that a spate of cancer among the region's leaders could be a US plot – although he conceded he had no proof and did not want to make "reckless" accusations.

"I repeat: I am not accusing anyone. I am simply taking advantage of my freedom to reflect and air my opinions faced with some very strange and hard to explain goings-on," he said at the event, broadcast live on state television.

Recent years have seen a series of leftwing Latin America leaders diagnosed with cancer including Brazil's current president, Dilma Rousseff, Paraguay's Fernando Lugo, and the former Brazilian leader Luiz Inácio Lula da Silva.

In late June Chávez admitted he was also being treated for cancer, telling Venezuelans that doctors had removed "cancerous cells" from his body.

"I don't know but … it is very odd than we have seen Lugo affected by cancer, Dilma when she was [presidential] candidate, me, going into an election year, not long ago Lula and now Cristina," Chávez said this week.

"It is very hard to explain, even with the law of probabilities, what has been happening to some leaders in Latin America. It's at the very least strange, very strange," the Venezuelan president said, according to government radio Radio Nacional de Venezuela.

Despite his lack of evidence Chávez hinted that other Latin American leaders should watch out – and recalled how US doctors could have infected 2,500 Guatemalans with STDs during the 1940s.

"Evo take care of yourself. Correa, be careful. We just don't know," he said, referring to Bolivia's first indigenous president, Evo Morales, and Rafael Correa, the president of Ecuador.

Chávez said he had received words of warning from Cuba's former leader Fidel Castro, reputedly the target of dozens of failed and often bizarre assassination plots including a fungus-infected diving suit and an exploding cigar.

"Fidel always told me, 'Chávez take care. These people have developed technology. You are very careless. Take care what you eat, what they give you to eat … a little needle and they inject you with I don't know what,'" he said.

While Venezuela's economy remains closely bound to the United States– the South American country exports more than 800,000 barrels of oil there each day – Chávez's colourful attacks on the Washington have been a regular fixture of his presidency.

Apart from the regular insults hurled at its leaders, Chávez has also accused the US of plotting to invade his country and involvement in a 2002 coup attempt that briefly toppled him from power.

In July this year Evo Morales floated a conspiracy theory of his own, suggesting the CIA might deliberately plant drugs on Bolivia's presidential plane in order to discredit his government.

"Do you know what? I think they have to be preparing something," he said. "So much [so] that I'm afraid to go with our airplane to the United States."

Source: guardian.co.uk