A huge voter turnout swamped polling sites across Venezuela on Sunday as a united, well-organized opposition candidate gave President Hugo Chavez the race of his life.

Tensions rose in the bitterly divided country while an undetermined number of voting stations remained open after the official 6 p.m. closing time, with not a single result announced nearly three hours later.

Chavez, a socialist who has ruled for nearly 14 years, called on Venezuelans to await results patiently, speaking briefly Sunday night by phone during a news conference held by his campaign chief.

Electoral officials gave no indication of when they might begin releasing first returns. Exit polling is forbidden in Venezuela.

The electoral council's president, Tibisay Lucena, said any stations where voters had not cast ballots would remain open. Meanwhile, bands of red-shirted pro-Chavez motorcyclists, honking horns, roved central Caracas ensuring that such stations stayed open.

While not accusing the government of an intentional delay, challenger Henrique Capriles complained via Twitter that most voting stations lacked lines and that the government should get on with the vote-counting.

Capriles spokesman Armando Briquet demanded that all motorcycle traffic be banned. In the past, gangs of red-shirted motorcyclists chanting pro-Chavez slogans have intimidated people.

Chavez's campaign manager, Jorge Rodriguez, told reporters there were no such plans. "This country has freedom of circulation," he said at a news conference.

Capriles has united the opposition in a contest between two sides that distrust each other so deeply that some expressed concerns whether a close election result would be respected.

If Chavez wins, he gets a free hand to push for an even bigger state role in the economy, further limit dissent and continue to befriend rivals of the United States.

With a Capriles win, an abrupt foreign policy shift can be expected, including halting preferential oil deals with allies such as Cuba, along with a loosening of state economic controls and an increase in private investment. A tense transition would likely follow until the January inauguration because Chavez's political machine thoroughly controls the wheels of government.

"We will recognize the results, whatever they are," Chavez told reporters after casting his vote in Caracas. He said he was pleased by the "massive turnout."

The stakes in the country with the world's largest known oil reserves couldn't be higher.

At many polling places, voters started lining up hours before polls opened at dawn, some snaking blocks in the baking Caribbean sun. Troops guarded thousands of voting centers across the country.

Defense Minister Henry Rangel Silva said as he voted that all had been calm and he hoped that would continue. He said if any groups try to "disturb order, they should know there is an armed force prepared and equipped and trained ... to put down any attempt at disturbances."

He didn't identify the groups to which he was referring.

The 40-year-old Capriles, a wiry former governor affectionately called "Skinny" by supporters, infused the opposition with new optimism, and opinion polls pointed to him giving Chavez his closest election.

Some recent polls gave Chavez a lead of about 10 percentage points, while others put the two candidates about even.

Chavez spoke little during the campaign about his fight with cancer, which since June 2011 has included surgery to remove tumors from his pelvic region as well as chemotherapy and radiation treatment. He has said his most recent tests showed no sign of illness.

"Chavez is going to fight until his last breath. He doesn't know how to do anything else," said Antonio Padron, a bank employee backing the president. Padron expressed optimism that the 58-year-old Chavez would win but predicted a close finish: "It's a tough fight. The opposition has never been this strong."

Chavez won the last presidential vote in 2006 with 63 percent of the vote.

A former army paratroop commander first elected in 1999, Chavez has presided over an oil boom and has spent billions of dollars on social programs ranging from cash benefits for single mothers to free education.

But he has suffered declining support due to one of the world's highest murder rates, 18 percent inflation, a deteriorating electrical grid and a bloated government accused of endemic corruption and mismanagement.