Leftist ex-military man Ollanta Humala has claimed victory in Peru's presidential runoff after a tight, polarized campaign against Keiko Fujimori, daughter of a jailed former strongman.

"We've won the elections in Peru," Humala shouted over a cheering crowd of supporters in central Lima late Sunday, many waving red and white Peruvian flags, as final results trickled in.

Official results showed his slight lead over his right-wing rival Fujimori creep upwards after quick counts by three polling companies predicted it would be between two and 4.4 percent.

Humala's victory "is irreversible," Manuel Saavedra, director of pollster CPI, told AFP earlier.

A downbeat Fujimori told a crowd of supporters on Sunday night: "If the ONPE (electoral authority) ratifies the quick count, I'll recognize the results."

Both Humala, 48, and Fujimori, 36, drew support with populist promises to help around one third of the population of 29 million still living in poverty despite Peru's record growth on the back of mineral exports in the past decade.

Many remaining votes from remote Andean provinces were expected to favor Humala over Fujimori, who drew a chunk of support from a conservative, city-dwelling elite in the nation stretching from the Amazon to the Pacific.

Humala promised to share out Peru's mineral wealth -- including gold, silver and copper -- and sought to play down his former ties to anti-liberal Venezuelan President Hugo Chavez while turning toward Brazil's more moderate left.

He promised Sunday to "continue with economic growth, and this growth will be the great motor of social development in the country."

"It's great that people are coming out of the lethargy of the past 50 years to realize that the economic powers benefit from the weakness of the poor and dictate the political agenda," said 46-year-old Mario Aguirre as he celebrated the result in central Lima.

But after a bitter campaign, many Peruvians were faced with a choice for the "lesser of two evils" after the two most extreme candidates won an April first round.

Keiko Fujimori campaigned in the shadow of her father, Alberto Fujimori, who is serving a 25-year jail term for corruption and rights abuses during a 1990s crackdown on extreme leftist Shining Path and Tupac Amaru guerrillas.

She courted the business community and most of the media with promises of keeping the free-market model which has helped make Peru one of Latin America's fastest growing economies.

But the former 19-year-old "first lady" also provoked fears of following her father's authoritarian path or seeking to free him.

Humala's win will be the first return of the left to power in Peru since the 1968-1975 military regime of Juan Velasco Alvaredo.

It created uncertainty after his rise -- and his promises of more control of the mining sector -- sent shockwaves through the stock exchange. He moderated his platform several times during the campaign.

Humala first came to prominence in 2000 when he led a short-lived military rebellion at the end of Alberto Fujimori's 1990-2000 elected presidency. He has also been accused of rights abuses which have never been proven.

Both candidates sought to remove doubts over their credibility in the polarized race.

Humala was set to take over from President Alan Garcia on July 28.

He will face tough negotiations over his political platform in the Congress, where his nationalist party only has 47 seats out of 130.

Five soldiers deployed to provide election security were killed and six hurt in an attack on Saturday blamed on remnants of the Shining Path linked to drug traffickers in southeast Peru.