Six people have died in election rioting in the Indonesian capital, authorities said Wednesday, as supporters of the losing presidential candidate burned vehicles and battled police and the government announced restrictions on social media.

Subianto, a volatile ultra-nationalist politician, has refused to accept the official results of the April 17 election and instead declared himself the winner. The Election Commission on Tuesday said President Joko Widodo, the first Indonesian president from outside the Jakarta elite, had won 55.5 per cent of the vote, securing the moderate technocrat a second term. Subianto, an elite figure from a wealthy family connected to former dictator Suharto, also lost to Widodo in 2014. He has made four unsuccessful bids for the presidency since Suharto was ousted in 1998.

Rudiantara, the communications and information technology minister, said features of social media including Facebook, Twitter and WhatsApp will be restricted on a temporary basis to prevent the spread of hoaxes and inflammatory content. He said messaging systems will still work for text and voice messages but photos and videos will be blocked or slowed.

National police chief Tito Karnavian said the people who died in the rioting were hit by gunshots or blunt devices. Authorities are still investigating the death causes and are not ruling out the involvement of third parties acting as provocateurs.

"There are attempts to create martyrs, blaming security officials for building public anger," he said.

The rioting in Jakarta was planned and not spontaneous, according to police. Officers found an ambulance filled with stones and some of the dozens of people arrested had envelopes of money, said national police spokesman Muhammad Iqbal. Many of those arrested and come from outside Jakarta, he said.

The government had deployed some 50,000 police and soldiers in Jakarta in anticipation of protests following the official election results. Many residents have left the city and parts of the downtown are closed to traffic with the election supervisory agency and Election Commission barricaded with razor wire.

In the past week, authorities have arrested three pro-Subianto activists on suspicion of treason. They included Sunarko, a retired general and former commander of Indonesia's special forces who uses a single name. Police allege there was a plot to seize crucial government buildings in Jakarta.

Subianto's campaign plans to challenge the election in the Constitutional Court. They allege massive fraud in the world's third-largest democracy but have provided no credible evidence.

The former special forces general and members of his campaign team had said they would mobilize "people power" during days of street protests. The former general has also called on supporters to refrain from violence.

Subianto ran a fear-based campaign, emphasizing what he sees as Indonesia's weakness and the risk of exploitation by foreign powers or disintegration. He aligned himself with hard-line Muslim groups and won massive majorities in conservative provinces such as Aceh, which follows Shariah law, but was defeated by Widodo in the president's populous East Java and Central Java strongholds.

Widodo's campaign highlighted his progress in poverty reduction and improving Indonesia's inadequate infrastructure with new ports, toll roads, airports and mass rapid transit.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)