World leaders mourn Chavez's death

A US military spokesman said it was aware of the cancer-related allegations and that one of the expelled diplomats, Colonel David Delmonico, was "en route back to the United States".

In fact, it was not the first time that Venezuela accused its "enemy country", clearly referring to the United States, for being responsible for Chavez's cancer, and those of several other leaders in the region.

Back in late 2011, Chavez speculated that the United States might have developed a way to inoculate Latin American leaders with cancer.

Apart from Chavez, a string of leaders in the region, including Paraguay's Fernando Lugo, Brazil's Rousseff and former Brazilian leader Luiz Inacio Lula da Silva, have all been diagnosed with the deadly disease.

However, the United States promptly denied the allegation, saying it was "reprehensible".

During his stay in power over the last 14 years, Chavez has regularly lashed out at the US government for trying to destabilize his government. And the two countries have not exchanged ambassadors over the past two years.

Also in the West, Canadian Prime Minister Stephen Harper offered condolences to Venezuela, saying his country hopes to work with Chavez's successor to build a region which is "more prosperous, secure and democratic."

"At this key juncture I hope the people of Venezuela can now build for themselves a better, brighter future based on the principles of freedom, democracy, the rule of law and respect for human rights," Harper said.

In London, British Foreign Secretary William Hague said he was "saddened" by the death, saying the Venezuelan leader had left a "lasting impression" on his people.

In a statement, French President Francois Hollande praised Chavez for his determination "to fight for justice".

"The late president expressed, while his temperament and the positions he took were not shared by everyone, an undeniable wish to fight for justice and development," the statement said.

Hollande added that he is sure that Venezuela will overcome this test of its democracy and stability.

Chavez was first diagnosed of cancer in his pelvic region in June 2011.

Though he won his third straight term as president of the country late last year, cancer had forced him to delay the inauguration.

Under the Venezuelan constitution, an election has to be held within 30 days if the president is pronounced unfit to return to power.

Venezuela's opposition factions have already been in talks to pick a candidate once an election is called.