Ms Rachmawati Sukarnoputri, a daughter of Indonesia's founding president Sukarno, has been arrested for alleged treason.
The 66-year-old was picked up yesterday along with nine other suspects in a pre-dawn operation, hours before a mass protest against Jakarta Governor Basuki Tjahaja Purnama for blasphemy.
National police spokesman Boy Rafli Amar said the suspects were planning to take advantage of the rally to subvert the government.
Another spokesman, Colonel Rikwanto, said there was sufficient evidence to charge eight of the suspects with makar, the local slang for trying to overthrow the government. The other two faced charges for spreading hatred, he added.
Both spokesmen did not name the suspects but Ms Rachmawati's lawyer, Mr Aldwin Rachardian, told Tempo news yesterday afternoon that she had been arrested in connection with allegations that she was part of a group plotting a coup.
Mr Aldwin also said politician and rock musician Ahmad Dhani and activist Ratna Sarumpaet were also being held for questioning.
Three others named by local media, citing confidential sources, were retired generals Kivlan Zein and Adityawarman, and former lawmaker Sri Bintang Pamungkas.
A source familiar with the investigations told The Straits Times that the suspects were prominent political figures and activists, including some who have been vocal against President Joko Widodo and Mr Basuki, a close ally.
Under Indonesian law, a person found guilty of treason could face life in prison.
Col Rikwanto declined to provide details on the case, saying only that investigations are ongoing.
He also said the decision to arrest the 10 suspects was based on evidence gathered by investigators over the last month.
"The police by law have 24 hours to interrogate the 10 who have been arrested and decide whether to detain any of them further," he added.
The suspects were rounded up between 3am and 6am yesterday, as tens of thousands of Muslims were making their way to the National Monument in downtown Jakarta to protest against Mr Basuki, better known as Ahok.
The anti-Ahok protest is the third organised by the National Fatwa Guardians of the Indonesian Ulema Council (GNPF-MUI) and led by the Islamic Defenders Front (FPI).
The first one took place in October, just weeks after the Chinese- Christian politician was accused of telling voters not to be misled by his opponents, who cited a verse in the Quran to urge Muslims not to vote for a non-Muslim.
The second one, on Nov 4, which saw about 100,000 protesters, many of them from outside Jakarta, began peacefully but turned into a riot later at night.
Mr Joko and National Police chief Tito Karnavian accused dissident elements of being behind the protest. They also hinted that "political actors" could be using the rallies to destabilise the government.
Ms Rachmawati is the younger sister of former president Megawati Sukarnoputri, who heads the ruling Indonesian Democratic Party - Struggle (PDI-P).
She was also a senior adviser to the Nasdem Party, which is part of the ruling coalition and backed by the PDI-P. She was sacked from Nasdem after she declared her support for former army general and Gerindra Party candidate Prabowo Subianto in the 2014 presidential election.
