By Jessica Damiana and Fransiska Nangoy

JAKARTA — Defeated Indonesian presidential candidate Prabowo Subianto is set to lodge a challenge to the result of the April 17 election in the Constitutional Court on Friday after complaining that the vote was rigged.

President Joko Widodo won 55.5% of votes in the poll to lead the world's third biggest democracy, beating retired general Prabowo, who got 44.5%, the General Election Commission (KPU) said on Tuesday.

After the announcement, Prabowo repeated earlier claims that there had been widespread cheating in favor of the incumbent and thousands of his supporters demonstrated in the capital this week to protest against the result.

Eight people were killed, including three teenagers, while 737 were hurt in two nights of rioting, Jakarta Governor Anies Baswedan said.

The election agency has said there was no evidence of systematic cheating and independent observers have said the poll was free and fair.

"The process of submitting the dispute lawsuit and other legal efforts are steps to ensure that we can carry election results that are free and fair," Prabowo's running mate, Sandiaga Uno, told reporters.

He said people had "witnessed with their own eyes" that the polls were unfair.

An exit poll conducted by pollster Indikator Politik Indonesia on election day showed that 94% of voters believed the election had been free and fair.

Police have arrested hundreds of people accused of taking part in the riots or provoking violence, two of whom were members of a militant group that had pledged support for Islamic State, national police spokesman Muhammad Iqbal said.

Police had also found envelopes containing money, suggesting instigators had paid some of the rioters, Iqbal said, adding that tests showed some of the suspects had taken the stimulant methamphetamine.

Dozens of protesters started to gather near the Constitutional Court on Friday afternoon in anticipation of Prabowo's arrival.

Widodo has warned of tough action against those instigating riots, while Prabowo has called for peaceful protests and restraint.

Jusuf Kalla, Widodo's vice president, met Prabowo on Thursday, Prabowo's campaign team said without elaborating.

The court expects to hold a first hearing on the dispute after the Eid Al-Fitr holiday, which is in the first week of June, and to deliver a verdict on June 28, spokesman Fajar Laksono said.

Prabowo also lost the 2014 presidential election to Widodo by a slimmer margin and had objected to that result, lodging a complaint with the Constitutional Court that was rejected.

The government has deployed 58,000 police and soldiers across Jakarta to maintain security and put temporary blocks on some social media to prevent unrest sparked by fake news. — Reuters