Right-leaning Keiko Fujimori is backed by the business community and poor women [Reuters]

Keiko Fujimori, the daughter of jailed former President Alberto Fujimori, has a thin edge over rival Ollanta Humala a week before Peru's June 5 presidential run-off election, three polls have shown.

Right-leaning Fujimori had 50.5 per cent of the vote on Sunday while left-leaning Humala, a former army officer, had 49.5 per cent in a mock nationwide vote organised by Ipsos.

The survey of 1990 people was conducted on May 21-27 and has a margin of error of 2.2 percentage points.

In another mock vote, by CPI, Fujimori had 51.8 per cent and Humala had 48.2 per cent.

CPI surveyed 2,800 people on May 25-28 and its margin of error was 1.85 percentage points.

Fujimori had a larger lead in another poll by Datum, getting 52.3 per cent of the vote to Humala's 47.7 per cent.

The survey of 5,019 people from May 23-25 has a margin of error of 1.4 percentage points.

Market worries

Fujimori, 36, is backed by the business community and poor women. Her father was credited with opening the economy to trade and taming hyperinflation in the 1990s, but his government fell amid allegations of corruption and human rights scandals in 2000 following a tough crackdown on guerrillas.

Humala, 48, has tried with limited success to distance himself from his former political mentor, Venezuela's socialist President Hugo Chavez, and present himself as a moderate like Brazil's popular former president, Luiz Inacio Lula da Silva.

Humala, who once led a bloodless insurrection to demand the elder Fujimori step down, has promised to prudently manage the surging economy, though critics fear he would roll back years of free-market reforms.

Peru's currency, the sol, and stocks plunged after Humala won the first-round vote on April 10 as investors worried he would intervene in the economy and hurt private investment.

Financial asset prices later recovered as Fujimori rose in polls. Humala has revised his government plan to make it more attractive to investors, dropping a controversial tax increase and a proposal to take over private pension funds.