JAKARTA (Reuters) - Indonesian President Joko Widodo on Thursday declared victory in a presidential election to lead the world’s third-largest democracy but his challenger also claimed he had won and complained of widespread cheating.

Unofficial results from private pollsters based on vote samples from Wednesday’s election pointed to a comfortable win for Widodo, with about 55 percent of the popular vote, giving him a lead of almost 10 percentage points over his rival, former general Prabowo Subianto.

The counts from reputable pollsters have proved to be accurate in previous elections, though the official result will not be announced until May 22.

Widodo told reporters he had received congratulatory calls from 22 state leaders, including Malaysian Prime Minister Mahathir Mohamad and Turkish President Recep Tayyip Erdogan, and he had invited his rival to meet.

Widodo also urged supporters to wait for official results to confirm the win.

At a separate news conference just minutes after Widodo declared victory, Prabowo appeared defiant and said his team had evidence of cheating and claimed to have won 62 percent of the popular vote based on internal polling.

“We have declared (victory) because we got evidence of widespread cheating at the village, sub-district and district levels across Indonesia,” he said, standing next to his running mate, Sandiaga Uno, who looked more subdued.

In 2014, Prabowo had also claimed victory on election day, before contesting the results at the Constitutional Court, which confirmed Widodo’s win.

A spokesman for Praboow said he would take his complaint to the Constitutional Court if the Election Commission confirmed Widodo’s victory.

The commission said earlier on its website Widodo had secured about 50 percent of the vote, based on results from 808 of more than 800,000 polling stations, with Prabowo on about 45 percent.

The English-language Jakarta Post newspaper carried a front-page headline declaring “Five More Years” next to a picture of the president.

Financial markets surged early on Thursday on Widodo’s apparent victory, though gains were pared in the afternoon. The rupiah currency ended the day up 0.3 percent from the previous close, and the Jakarta stock index - at one point up 2.4 percent - closed 0.4 percent higher.

‘NO CASE’

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Alexander Raymond Arifianto, a political analyst at the S. Rajaratnam School of International Studies (RSIS) in Singapore, said Widodo’s margin of victory meant the opposition did not appear to have a strong case to claim the election was stolen.

But he noted risks that Islamist supporters of the challenger, including the hardline Alumni 212 movement, could hit the streets to dispute the election.

“So Prabowo has no case, but the hardliners and Alumni 212 can create lots of headaches for Jokowi if they go ahead with their protest plan tomorrow and in future weeks,” he said, referring to president by his nickname.

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Novel Bamukmin, a spokesman for Alumni 212, said the movement planned a peaceful march after Friday prayers at Jakarta’s Istiqlal mosque.

“We just want to bow down to express our gratitude in order that this victory is recognised,” he said, referring to Prabowo’s claim he won the election.

Islamist groups have in the past been able to mobilize tens of thousands of supporters.

From late 2016, they organised a series of big protests against the Jakarta governor, Basuki Tjahaja Purnama, the first ethnic-Chinese Christian to hold the job, who was subsequently jailed for insulting the Koran.

Police vowed firm action against any rallies that could disturb security as Prabowo’s supporters planned to march in central Jakarta after midday prayers on Friday.

“I appeal to anyone not to mobilize, whether to mobilize people to celebrate victory or mobilize due to dissatisfaction,” said national police chief Tito Karnavian, pledging firm action.

At the same news conference, chief security minister Wiranto called for people to avoid “any act of anarchy that breaches the law”.