Condolences poured in Wednesday from world leaders who had found common cause with Venezuela's Hugo Chavez in his 14-year campaign to galvanize the Latin American left and defy US "imperialism."

Ideological allies in Latin America lined up to salute the late firebrand as Russia, China and Iran paid tribute to a key regional partner, while the United States expressed hope for improved ties with oil-rich Venezuela.

Chavez, 58, died after a long battle with cancer, plunging Venezuela into an uncertain future after 14 years of rule by the charismatic former paratrooper, a standard-bearer of Latin America's "anti-imperialist" left.

Cuba hailed Chavez as a "true son" to the communist nation's retired 86-year-old revolutionary icon Fidel Castro and declared three days of mourning in honor of its closest regional ally and main economic benefactor.

Russian President Vladimir Putin called Chavez an "uncommon and strong man who looked into the future and always set the highest target for himself" and thanked him for laying the "solid basis" for Russia-Venezuela relations.

Russia enjoys close military ties with Venezuela, which also represents one of the main oversees investment targets of the giant state oil company Rosneft.

China, which also cultivated strong economic ties with Chavez's Venezuela, called him a "great leader" and a "great friend of the Chinese people."

Iranian President Mahmoud Ahmadinejad said Chavez had fallen as a "martyr" to a "suspect illness," apparently referring to claims by Chavez's successor Nicolas Maduro that the cancer that killed him was part of a conspiracy.

"Venezuela lost its brave, strong son and the world lost a wise and revolutionary leader," Ahmadinejad added.

"I have no doubt that he will return, along with the righteous Jesus and the perfect human," a reference to Shiite Islam's 12th imam, which Iran's majority faith believes will return with Christ to bring peace and justice to the world.

Washington's response to the death of Chavez, who had repeatedly thumbed his nose at the United States and referred to president George W. Bush as a "donkey" and the "devil," was more circumspect.

"At this challenging time of President Hugo Chavez's passing, the United States reaffirms its support for the Venezuelan people and its interest in developing a constructive relationship with the Venezuelan government," President Barack Obama said in a short statement.

"As Venezuela begins a new chapter in its history, the United States remains committed to policies that promote democratic principles, the rule of law, and respect for human rights."

UN Secretary General Ban Ki-moon paid tribute to Chavez's work on behalf of his country's poor and his support of Colombia's peace process, saying he "spoke to the challenges and aspirations of the most vulnerable Venezuelans."

Latin American leaders -- even those ideologically at odds with Chavez -- praised him as a strong leader who had worked to unify the region.

Brazilian President Dilma Rousseff said Chavez was a "great Latin American... a great leader, an irreparable loss and above all a friend of Brazil."

In Argentina, Vice President Amado Boudou said on Twitter that "all of Latin America" was in mourning. "One of the best has left us: you will always be with us, Comandante," he said.

Colombian President Juan Manuel Santos, who had cultivated improved ties with Venezuela in recent years, said Chavez's death was "a great loss for Venezuela and the region, for Colombia and for me personally."

Chilean President Sebastian Pinera, a conservative billionaire, called Chavez a leader who was "deeply committed to Latin America's integration," and Mexican President Enrique Pena Nieto offered "deep condolences."

Bolivia's socialist President Evo Morales -- whose political priorities and style of leadership have been inspired by Chavez -- said he was "crushed" by his friend's death and would soon travel to Venezuela.

"We are in pain," Morales added.

Ecuadoran President Rafael Correa, another close ally, said Chavez's death was an "irreparable loss" for Latin America.

Nicaraguan leader Daniel Ortega, heavily reliant on Venezuelan aid, vowed to continue "waging the battles" of Chavez.

French President Francois Hollande praised Chavez's determination "to fight for justice," saying he had "profoundly marked his country's history."

British Foreign Secretary William Hague said he was "saddened" by the death, saying Chavez had left a "lasting impression" on Venezuela's people. Germany also offered condolences, saying it hoped Venezuela would embrace democracy.

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