Indonesian presidential candidate Anies Baswedan plans to contest the results of last month's election.
He told reporters on Wednesday that he would file a case at Indonesia's Constitutional Court.
Unofficial results show Defense Minister Prabowo Subianto winning with more than 55% of votes in the three-way race. The official results are expected to be released by March 20, Reuters reported.
He had the backing of current President Joko Widodo and Baswedan says there was government interference in the election.
"We plan to file to the MK for sure but the content is not something that we can disclose," Baswedan said.
He has complained about what he called irregularities in the months leading up to the election, including a huge increase in social assistance in key electoral regions.
"We want to make sure that irregularities don't go unchecked," he said.
The Constitutional Court typically handles election disputes but Indonesia's parliament has the power to investigate certain regulations and the conduct of public officials, including the president.
Human rights groups have claimed that Subianto was involved in a series of human rights violations in the 1980s and 90s as a member of the military. Subianto has denied those allegations.
