By Diego Ore and Eyanir Chinea

CARACAS (Reuters) - Hundreds of thousands of Venezuelan opposition supporters rallied in a staunchly pro-government part of the capital on Sunday, answering a call by their candidate Henrique Capriles and showing strength a week before the presidential election.

"Today the streets of Caracas are full of happiness and hope, confirming what will happen next Sunday," Capriles, the 40-year-old governor of Miranda state, told the crowd.

He faces acting President Nicolas Maduro, who has vowed to continue the hardline socialism of his late boss, Hugo Chavez, if he wins the April 14 election. Maduro held a huge rally on Sunday in rural Apure state, on the Colombian border.

More often seen filled with the red flags and T-shirts of Chavez's loyal supporters, the capital's historic Bolivar Avenue was packed with opposition supporters decked out in the blue, yellow and red of Capriles' campaign.

"We're winning this process," Capriles said, sweating under the hot sun in a burgundy-colored shirt, rosary beads around his neck and a baseball cap in the colors of Venezuela's flag.

He said that the day following his election victory would be one of peace and reconciliation among all Venezuelans, and he addressed supporters of Maduro's government directly.

"Those who put on a red shirt today, I just ask you: open your eyes! I'll work hard, I'll shed skin, to win your trust."

Despite the opposition leader's optimism, opinion polls give Maduro a lead of more than 10 percentage points.

Opposition supporters marched from different parts of the city to converge on the avenue, where they waved flags, cheered and sang.

Around the edges of the rally, groups of red-clad "Chavista" pro-government supporters chanted in favor of Maduro.

Both candidates are touring the South American country during a lightning, 10-day campaign ahead of next Sunday's vote, which was triggered by Chavez's death from cancer on March 5.

It has been a bitter run-up to the election, with deeply personal attacks and accusations of dirty tricks by both sides.

'VALUE OF LOYALTY'

The race took a somewhat surreal turn on Saturday when Maduro said a centuries-old curse would fall on the heads of those who do not vote for him.

Maduro, 50, was a bus driver and union leader who rose to become Chavez's foreign minister, then vice president.

At his rallies, he frequently refers to Chavez in adoring terms and plays a video from December where the former president endorsed Maduro as his successor.

"He taught us the supreme value of loyalty. With loyalty, everything is possible. Betrayal only brings defeats and curses," Maduro told cheering supporters on Sunday.

Maduro again accused the opposition of hatching a plot to assassinate him.

He has also accused the U.S. government of planning to kill Capriles and blame it on his government in order to spark unrest before the election. Washington denied it.

Capriles has ridiculed Maduro's claims and likened them to Chavez's frequent denunciations of "imperialist" assassination plots during his 14-year rule.

The opposition says the assassination claims are designed to distract voters from daily problems such as violent crime, high prices and creaking public services.

Capriles, who is predicting a late pro-opposition surge as sympathy wears off after Chavez's death, is vowing to install a Brazilian-style administration of free-market economics with strong social welfare policies.

Capriles mocks Maduro as a bad copy of Chavez, and says his decisions as acting president caused a currency devaluation and price spikes that have been disastrous for Venezuelans.

Gisela Quijada, a 68-year-old nurse attending the opposition rally in Caracas, said the country was broken.

"I like Capriles ... the other one is immature. He just wants to be a copy of Chavez," she said.

"Chavez was a leader for them. I can't deny it. But he (Maduro) has nothing in his head. If Capriles doesn't win, we'll keep on fighting for him. But we're sure he's going to win!"

The election will decide the future of "Chavismo" socialism and control of the world's biggest oil reserves and economic aid to left-leaning nations across Latin America and the Caribbean.

(Writing by Daniel Wallis; Editing by Philip Barbara and Stacey Joyce)