Venezuelan president Hugo Chavez has questioned whether the United States has developed a secret technology to give cancer to left-wing leaders in Latin America.
Mr Chavez, who himself had cancer treatment this year, was speaking the day after it was announced that Argentina's president, Cristina Fernandez de Kirchner, also has the disease.
The BBC reports that Fernando Lugo of Paraguay, Dilma Rousseff of Brazil and her predecessor Lula da Silva have also been treated for cancer.
Mr Chavez said this was "very strange" but stressed that he was thinking aloud rather than making "rash accusations".
But he said the instances of cancer among Latin American leaders were "difficult to explain using the law of probabilities".
"Would it be strange if they had developed the technology to induce cancer and nobody knew about it?" Mr Chavez asked in a televised speech to soldiers at an army base.
Mr Chavez noted that US government scientists had infected Guatemalan prisoners with syphilis and other diseases in the 1940s, but that this had only come to light last year.
And he joked that he would now take extra care of the presidents of Bolivia and Ecuador - Evo Morales and Rafael Correa - lest they also be diagnosed with cancer.
The Venezuelan leader, who is 57, has often accused the US of plotting to overthrow or even kill him.