Both candidates claimed victory in Indonesia's presidential election on Wednesday, suggesting there could be a drawn out constitutional battle to decide who will next lead the world's third-largest democracy.

Just a few hours after voting closed, Jakarta governor Joko "Jokowi" Widodo said he had won, based on quick counts of more than 90 percent of the votes. A victory for him would be seen as a triumph for a new breed of politician that has emerged in Southeast Asia's biggest economy, and increase the promise of desperately needed reform in government.

But ex-general Prabowo Subianto, the rival candidate viewed as representative of the old guard that flourished under decades of autocratic rule, said other, unnamed, quick counts of votes favoured him.

Jokowi, on other hand, named tallies by six pollsters, most regarded as reliable and independent. The included three respected, non-partisan agencies - CSIS, Kompas and Saifulmujani - which provided accurate tallies in the April parliamentary election.

The quick counts are conducted by private agencies which collate actual vote tallies as they come out of each district. The results however are unofficial: the Election Commission will take about two weeks to make an official announcement and the new president is not due to take office until Oct. 1.

"There are many quick counts from various survey agencies. But...the one that will be valid according to law in the end will be the verdict of the KPU (Election Commission)," Prabowo told a talk-show on a television channel.

A senior aide to Jokowi said the party would not take any action like naming a cabinet until the official result is announced on or around July 22.

"We've waited months. We can wait another 2 to 3 weeks for the (Election Commission's) final verdict," Luhut Panjaitan told Reuters.

The standoff is unprecedented in Indonesia, a member of the G-20 group of nations that is holding only its third direct presidential election. In both the previous elections, Susilo Bambang Yudhoyono, now the outgoing president, won by a clear margin.

There have been concerns of violence once the result is known, a worry alluded to by Yudhoyono's administration.

"For both groups of supporters related with the split quick count results, we request they do not mobilise their supporters excessively," said Djoko Suyanto, coordinating minister for legal, political and security affairs.

There were no reports of any major violence. Around 250,000 police officers were on standby across Indonesia, authorities said.

Claim and counter-claim

It has been the dirtiest and most confrontational campaign in memory in a country which traditionally holds up the value of consensus politics.

Ahead of the vote, the two candidates had been neck and neck in opinion polls as Jokowi lost a huge early lead in the face of smear campaigns and a far more focused, and expensive, race for the presidency by his rival.

"Today the people have decided a new direction for Indonesia ... This is a new chapter for Indonesia," Jokowi told hundreds of supporters at Proclamation Square, where the country's first president Sukarno declared independence in 1945.

At the same time, Jokowi offered conciliatory words to his rival, Prabowo, saying he was a patriot and contributed to a better democracy.

Prabowo countered with his own declaration of victory.

"(The quick counts) show that we, Prabowo-Hatta, have received the support and mandate from the people of Indonesia," he told a rally in the capital, referring to his running mate Hatta Rajasa.

After the official result is declared, candidates can challenge the results in the Constitutional Court, the final arbiter over contested polls.

The Court's reputation has been badly tarnished after its chief was sentenced to jail for life this month for corruption.

"There have always been challenges...So we could end up with delayed certainty for a few weeks," Douglas Ramage, a Jakarta-based political analyst told Reuters.

The government declared Wednesday a public holiday and markets were closed although the rupiah currency hit a seven-week high against the dollar in offshore markets on Jokowi's victory claim.

His clean image is seen likely to bring in more foreign investment as he seeks to correct Indonesia's reputation of widespread corruption.

But any euphoria in the market could quickly evaporate if the stalemate over the result is not quickly resolved or if there is violence.

"Whether the market goes up or down tomorrow will mostly depend on the security. For me, maintaining security is very important at this point," said Isbono Putro, a director at BNI Asset Management, who helps manage about 8 trillion rupiah ($688.47 million) in assets.