JAKARTA, Indonesia — The police in Jakarta, Indonesia’s capital, have clashed with demonstrators as protests over the newly announced results of the April presidential election unraveled into violence.The city’s governor, Anies Baswedan, a close ally of the defeated presidential candidate Prabowo Subianto, cited reports of deaths and large numbers of injuries in the violence on Tuesday night, though they could not be immediately verified. Tito Karnavian, the chief of the Indonesian national police, also reported deaths, saying hospital officials had said six people were killed.Officials attributed the violence to organized groups bent on mayhem that appeared late Tuesday night after the day of political protest. But it was not immediately known which group those injured or killed belonged to. A police spokesman said 62 people had been arrested.In response to the unrest, the authorities said on Wednesday that they would block some social media services, including Facebook and Instagram, in some areas of the country.“I will not tolerate anyone who tries to disrupt security, disrupt the democratic processes and undermine the unity of this country that we very much love, especially rioters,” the newly re-elected president, Joko Widodo, told reporters.The violence was set off by Tuesday’s announcement, more than one month after the April 17 vote, that Mr. Joko had won re-election with 55.5 percent of the vote. The announcement inflamed some supporters of his opponent, Mr. Prabowo, who has accused election officials of widespread fraud and said he would legally challenge the result.Mr. Prabowo has not substantiated his claims of fraud, and international observers have not found evidence. In a statement on Wednesday, the United States Embassy in Indonesia called it “a successful, free and fair election.”But hundreds of Mr. Prabowo’s supporters rallied outside government buildings on Tuesday to protest the result.Television footage on Tuesday showed police officers in riot gear firing tear gas at demonstrators who hurled firecrackers back at the officers. Muhammad Iqbal, a national police spokesman, said the demonstrators were “provocative and violent,” according to Channel News Asia.“They damaged security barriers and provoked officers,” he said. “As per our standard operating procedure, officials pushed them back. The protesters were not cooperative and brutally attacked officers with rocks, Molotov cocktails and firecrackers.”Indonesia is the world’s third-largest democracy, and its election in April featured 800,000 polling stations spread across the archipelago for its population of about 260 million people.Faith politics figured prominently in the election, which pitted Mr. Joko, a moderate technocrat who has a reputation for celebrating diversity, against Mr. Prabowo, who is backed by some hard-line Islamists and is known as a ruthless former general and onetime son-in-law of the longtime dictator Suharto. Indonesia has the world’s largest Muslim population, but is a secular state with many religious minorities.