At least 25 other people were wounded Thursday when a suicide bomber and gunmen launched an attack near a Starbucks coffee shop, police said.
Four attackers were also killed, following the bombing and a firefight with police.
Among the 12 suspects subsequently rounded up in various Indonesian provinces, one is suspected to have received a money transfer from the alleged mastermind, Bahrun Naim, an Indonesian militant who authorities believed conducted the operation from ISIS' headquarters in Syria, national Police Chief Badrodin Haiti said.
The transfer helped finance Thursday's attack, the police chief said.
Police still are on high alert, Haiti said, in part because authorities have intercepted encoded messages about a possible attack. Further details about the threat weren't immediately available. Read more on edition.cnn.