Radical Islamist cleric Aman Abdurrahman, who allegedly ordered followers to mount the suicide attack in Jakarta on Jan 14 last year, was given special remission from his 10-year jail sentence, as part of Indonesia's 72nd Independence Day celebrations on Thursday.
But after his release from Nusakambangan prison last Sunday, the leader of the Jemaah Ansharut Daulah (JAD) militant group was picked up by counter-terrorism unit Densus 88, Law and Human Rights Ministry official Ibnu Chuldun told Tempo news on Thursday.
"Aman received remission, or a reduction of five months... but he was taken in by Densus 88 on Sunday, before his release letter was handed over," said Mr Ibnu.
More than 92,800 prisoners were given remissions of various lengths and released on Thursday as the country marked 72 years of independence from Dutch rule.
Aman was among 35 inmates jailed for terrorism-related offences to be released.
The Straits Times understands that the militant leader, who was also a key player in the Jemaah Islamiah (JI) terrorist network, is being held for questioning at a Densus 88 camp in Kelapa Dua in Tangerang regency, which is about an hour's drive from Jakarta.
Aman had pledged his allegiance to the Islamic State in Iraq and Syria (ISIS) while he was in jail. Besides his alleged role in last year's attack in the capital, he is also linked to several other terrorist attacks in Indonesia, including the twin suicide bombings in East Jakarta on May 23, which killed three policemen.
He was jailed in 2010 for funding a JI paramilitary training camp in Aceh and was expected to be released in December, although analysts had said he would be detained further for investigations into other terror acts he is alleged to have had a hand in from behind bars.
JAD, an offshoot of the JI group that was behind the 2002 Bali bombings, is known for mounting deadly attacks, especially on the Indonesian police.
In January, JAD and Aman were placed on a United States counter- terrorism watch list because of their ties to ISIS.
National police chief Tito Karnavian said previously that Aman would be charged over the Jan 14, 2016 attack, but investigators need to work fast to compile a case against him, or he could walk free in a matter of days.
The reason is that the police are allowed to hold a terrorist suspect only for a week because of Indonesia's weak anti-terror laws.
For months, Parliament has been deliberating proposed legislative changes to beef up the country's anti-terrorism Bill, first introduced in 2003 after the Bali attacks.
Among the proposed revisions are laws to allow the police to hold suspects involved in terror attack plots for up to six months, instead of a week, as well as making it an offence for citizens to join foreign militant groups such as ISIS in the Middle East or the Maute group, currently battling troops in the southern Philippine city of Marawi.