Police arrested an Indonesian, named as Arif Hodayatullah, near the capital for driving a car without a licence plate and found several books about bomb-making inside the vehicle, according to a document seen by AFP.
An anti-terror squad raided his house in West Java, where they arrested a Uighur, identified only as Alli, and confiscated a suicide vest and material to assemble a bomb.
"We also found a design (of where the attack would be carried out), but we have only found one, we need to investigate more," national police spokesman Anton Charliyan said late Thursday.
The arrests come at a time of heightened alert after police arrested several other suspected extremists.
On Monday police in Java arrested five suspects from a cell linked to the ISIS, and four from one linked to the Jemaah Islamiyah terror network, responsible for several major attacks in Indonesia.
The country is deploying more than 150,000 military and police personnel during the Christmas and New Year period and has increased security at its airports after a threat was directed at one serving Jakarta.
A police source, who declined to be named, said Alli was believed to be a bombmaker and was chosen to carry out the suicide attack.
Hodayatullah told police he was instructed by a man named Bahrunnaim, a militant residing in Syria, to help Indonesians wishing to join the ISIS group.
Indonesia, the world's most populous Muslim-majority country, suffered several major bomb attacks by Islamic radicals between 2000 and 2009, including the 2002 Bali bombings that killed 202 people.
But a crackdown has weakened the most dangerous extremist networks.
However the emergence of ISIS has sparked alarm that Indonesians returning from battlefields in the Middle East could revive them.
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