Panama was seen heading for the closest presidential election finish in decades, as the opposition battles to deny outgoing President Ricardo Martinelli a chance to keep an indirect hold over the booming Central American economy.

Recent polls put the three leading candidates - ruling party candidate Jose Domingo Arias, opposition politician Juan Carlos Navarro and Vice President Juan Carlos Varela - within a few points of one another on Sunday, in a race that pits an administration that oversaw a multi-billion dollar public works push against challengers from the left and right.

The winner inherits oversight of a major expansion of the Panama Canal, which was briefly stalled earlier this year after a row over costs between the canal and the building consortium.

The campaign has focused more on personalities than government policy, which is not expected to change dramatically regardless of who emerges as the winner, Reuters news agency reported.

Many voters voiced dissatisfaction with the ruling Democratic Change (CD) candidate, Arias, whose running mate Marta Linares, is Martinelli's wife and who is seen by opponents as a proxy for the outgoing president.

Martinelli's five-year presidency has been characterised by strong economic growth but also tarnished by allegations of corruption.

Panama canal revenue fails to tackle poverty

Challenges to tackle

An Arias win would make his party the first to gain re-election since a US invasion in 1989 to oust military strongman Manuel Noriega, who has been behind bars ever since.

Running neck-and-neck with Arias is moderate leftist challenger Navarro of the Democratic Revolutionary Party (PRD), a former mayor of Panama City.

Navarro is vowing to improve government transparency after Martinelli had to fend off allegations that the infrastructure contracts he handed out were tainted by corruption.

Trailing the other two candidates by a handful of percentage points is the Panamenista Party's Varela, the center-right vice-president. He helped Martinelli to win the presidency in 2009, but the two later fell out over his dismissal as foreign minister in 2011.

The winner faces the challenge of maintaining buoyant economic growth and ensuring the benefits trickle down in a land where a quarter of the population lives in poverty.

A banking and trading hub, Panama is best known for the canal that links the Atlantic and Pacific Oceans. Accounting directly for eight percent of gross domestic product, it has helped fuel the fastest growth in Latin America in the last few years.

At up to $624 a month, the minimum wage in Panama is among the highest in Latin America, but many of the country's poorest are feeling the bite of nagging inflation.

The discontent has led to a nationwide construction strike over pay since April 25. That has halted thousands of projects, including work on the canal expansion, which wasn’t well received by Martinelli, who will remain president until July 1.

Source: Agencies