Peru's bourse suspended trading two hours early and said it would not reopen until Tuesday after investors pushed the benchmark index12.5 percent lower in its biggest one-day fall ever. Traders said they wanted Humala to quickly send signals about who he will appoint to key policy making posts.

The local sol currency closed bidding 1.25 percent weaker at 2.791 per dollar, even after the central bank placed deposit certificates to curb its fall, its largest one-day fall since May 2009.

Official results gave Humala a narrow but growing lead of 2.5 percentage points over right-wing lawmaker Keiko Fujimori, the daughter of jailed former President Alberto Fujimori, who was favored by the business community.

Investors fear Humala could roll back free-market reforms as he campaigned on promises to fight poverty by redistributing the country's new-found wealth. He and his economic advisers have promised to run a balanced budget, fight inflation and respect private investment and Peru's many free-trade agreements.

Many investors still doubt whether his effort to moderate anti-capitalist views is sincere or a ploy to attract centrist voters.

"Until they define who the cabinet or the finance minister will be, there is going to be this uncertainty that is causing panic," said one local trader in Lima.

Shares of Credicorp, Peru's largest financial holding company, closed down 14.22 percent on the Lima benchmark index and were down 14.66 percent in New York.

Buenaventura, the country's top precious metals miner, fell 11.67 percent when trading was halted while its American Depository Receipts were down 12.44 percent. Humala is in favor of taxing windfall profits in the lucrative mining industry to fund social programs.

"We believe that mining concerns may see greater pressure than financials due to anxiety over increases in mining royalties," Deutsche Bank analysts wrote in a report.

KNEE-JERK REACTION?

Yields on sovereign bonds spiked while the cost of insuring Peruvian debt rose, with 5-year credit default swaps up 25 basis points to 170.5..

Some analysts say the initial market reaction to Humala's victory was overdone.

Humala, who does not have a majority in Congress, has struck a conciliatory tone since claiming victory and vowed an economic boom will continue. His chief economics adviser, Felix Jimenez, told Reuters late on Sunday there is no reason for investors to fear Humala's government plan.

"The economic proposals are entirely sensible, keeping macroeconomic balances, growth and creating conditions for domestic and private foreign investment," he said.

Another adviser, Kurt Burneo, a former central bank and finance ministry official, told Reuters on Monday that investors betting against Peru in financial markets "are going to lose."

JPMorgan is recommending investors look for buying opportunities in Peruvian debt.

"I think that there's probably going to be at this stage of the game more positive than negative surprises. We would frankly look for opportunities to add exposure. I think the market has probably overreacted a bit here," Joyce Chang, global head of emerging markets research at JP Morgan, told the Reuters 2011 Investment Outlook Summit on Monday.

Goldman Sachs advised clients that Humala is likely to appoint independents to key cabinet positions.