Venezuelan Vice President Nicolas Maduro says President Hugo Chavez has died.
The government announced Monday night that Chavez was in "very delicate" condition after suffering a new, severe respiratory infection.
Chavez anointed Maduro as his preferred successor before flying to Cuba in early December to undergo a fourth round of surgery for an unspecified cancer in his pelvic area.
The constitution calls for snap presidential elections in the event of Chavez's death. Chavez had presided over Venezuela for more than 14 years.
Venezuela's defense minister pledges the military will remain loyal to the constitution in the wake of his death.
Admiral Diego Molero appeared on national television to appeal for "unity, tranquility and understanding" among Venezuelans.
He says troops will safeguard the sovereignty of the country.
Hugo Chavez began his career at age 16, joining the Army as a paratrooper - 22 years later, believing the government was corrupt, he led a military coup to unseat the president.
It failed and Chavez was thrown in jail.
But years later as a politician, he campaigned to close the gap between the poor and the wealthy oil executives.
In 1998, he was elected President.
Four years later, a group of military officers staged a coup and put Chavez under arrest.
For two days, the newspapers announced Chavez was out. But troops loyal to Chavez staged a couter-coup putting him back in office.
Chavez believed the U.S. government secretly backed the coup and repeatedly threatened to stop supplying the U.S. with oil.
As one of the most outspoken critics of the U.S., he was friends with Cuba's Fidel Castro and Iran's Mahmoud Ahmadinejad. He particularly disliked President George W. Bush.
Chavez accused the U.S. President of neglecting the poor. So in 2005, the Venezuelan president announced that Citgo, the U.S.-based refining arm of his country's state run oil company would provide discounted heating oil to nearly 200,000 poor American households.
He hoped to have a better relationship with President Obama but a year after his election, Chavez called him a "poor ignoramous."
In 2011 Chavez was diagnosed with cancer.
He traveled to Cuba multiple times for surgery and was treated with chemotherapy.
In October of 2012 he won re-election, but just two months later he needed more surgery when the cancer returned.
Meanwhile, Venezuelans living in the United States are reacting with cautious optimism that there will be change in their homeland following President Hugo Chavez's death.
In the Miami suburb of Doral, Venezuelans watched on television as the country's vice president, Nicolas Maduro, announced Chavez had died Tuesday. At a popular restaurant, one person cheered at the news, but the rest watched quietly and refrained from any celebration.
Doral has the largest concentration of Venezuelans in the U.S. Dora's mayor and police chief prepared a security and contingency plan in the event of Chavez's death. Many Venezuelans are expected to gather at restaurants and meeting spots in Miami, though few people immediately showed up.
There are nearly 190,000 Venezuelans in the United States. Many are strongly anti-Chavez.