Jakarta on alert as Indonesia post-election protests turn violent

Policemen in Indonesia have fired tear gas to disperse demonstrators in central Jakarta, after supporters of losing presidential candidate Prabowo Subianto began setting fire to buildings and vehicles and pelted officers with rocks and burning objects.

National Police spokesman Dedi Prasetyo said protests against the final results of last month's presidential election, which showed Prabowo losing to incumbent President Joko Widodo, turned violent late on Tuesday and continued into the early hours of Wednesday.

He added that dozens of people had been detained.

KompasTV, an Indonesian news channel, showed protesters throwing rocks, facing off against hundreds of riot police in a neighbourhood in the centre of the capital.

Local media reported that some people had been hospitalised. There was no official confirmation about the injuries.

Prabowo, a retired general who has been accused of human rights abuses, has claimed widespread cheating in the April 17 election but has provided no credible evidence to back up his allegations.

The legal director of his campaign team said on Tuesday that Prabowo would lodge a formal challenge to the result with the Constitutional Court.

Several thousand people on Tuesday took to the streets around the office of the elections commission after the agency confirmed Widodo had won a second presidential term with 55.5 percent of the vote, compared with 44.5 percent for Prabowo.

Those protests ended peacefully, but the situation turned ugly when some demonstrators refused to leave the area.

Jakarta police spokesman Argo Yuwono said police used tear gas and water cannon against protesters who threw rocks, Molotov cocktails and burning objects. Earlier, some had set market stalls on fire.

Al Jazeera's Florence Looi, reporting from Jakarta, said the clashes went on for several hours, but the streets of the capital were calm on Wednesday morning.

Protesters were expected to return in the afternoon.

Prabowo has until Friday to lodge his appeal with the Constitutional Court. It then has 14 days from the time it receives all the evidence to make a decision.

"It's worth remembering that international observers have said the elections were largely free and fair, even though Prabowo alleges widespread cheating," Looi said.

"Some analysts have even said that because Widodo won by an 11 percentage point difference - translates some 17 million votes - this undermines Prabowo and the opposition's argument that the elections were rigged."

More than 30,000 troops have been deployed across the capital amid reports of protests after the publication of the official election results.

Tensions have also spiked since police said last week that they had arrested dozens of suspects linked to The Islamic State of Iraq and the Levant (ISIL or ISIS) who had planned to cause chaos by bombing post-election demonstrations.