Around 32,000 security personnel have been deployed across the Indonesian capital Jakarta after early "quick count" results confirmed Joko Widodo's victory in last month's elections.
Some schools have announced closures, while local offices have allowed staff to work, amid threats of protests by rival Prabowo Subianto's supporters.
The retired general, who was handed 44.5 per cent of the votes by the General Election Commission (KPU), "completely rejected" the results, and pledged to "continue to make legal efforts in line with the constitution to defend the mandate of the people".
Widodo, who won 55.5 per cent of the votes, said he will be a leader for all Indonesians.
"We are grateful and proud that amid our differences, we have been mature in keeping the peace," he said.
Hamas handed over three Israeli hostages on Saturday, whose emaciated appearance shocked Israelis following their release on live TV, in the latest stage of a ceasefire deal aimed at ending the 15-month war in Gaza.
The US Coast Guard in Alaska found the wreckage of a small plane atop frozen sea ice on Friday, after the aircraft suddenly lost altitude on Thursday and the crash killed all 10 people on board, officials said.
A US judge has temporarily allowed roughly 2,700 US Agency for International Development employees put on leave by President Donald Trump's administration to go back to work, pausing aspects of a plan to dismantle the agency.
Hamas accused Israel of multiple breaches of their ceasefire agreement on Friday, a day before the scheduled exchange of three more Israeli hostages for Palestinian prisoners in the latest stage in a fragile deal aimed at ending the war in Gaza.