The elite anti-terror squad working with regular police Thursday detained two men in Bandung on Java island and a third in the nearby area of Cimahi, and their houses were now being searched, said local police spokesman Yusri Yunus.
"We arrested three people in connection with the bombing, in three different locations yesterday afternoon," he told AFP.
The houses of the two suspected bombers are in the same area and had already been raided by authorities, who found Islamic teaching materials and bladed weapons.
The bombers attacked the busy terminal in the capital late Wednesday in a dramatic assault that sparked panic and left human body parts and shattered glass strewn across the street.
Three policemen were killed, while several other officers and civilians were injured in the assault at the Kampung Melayu terminal.
IS claimed responsibility through its propaganda agency Amaq, according to a statement carried by Site Intelligence Group late Thursday. Analysts have pointed the finger at local IS-linked group Jamaah Ansharut Daulah (JAD), which has been blamed for recent attacks.
The bus station bombing was the deadliest attack in Indonesia since January 2016, when a suicide blast and gun assault claimed by IS in downtown Jakarta left four attackers and four civilians dead.
Hundreds of radicals from Indonesia, the world's most populous Muslim-majority country, have flocked abroad to fight with IS, and the country has seen a surge in plots and attacks linked to the jihadists over the past year.
Twin bomb blasts kill at least three in Jakarta
Credible IS claim
Yunus would not reveal how the men arrested Thursday were suspected of being involved in the attack, saying only that authorities were led to the trio by witness testimony.
Police have said they believe that IS is linked to the attack, but have given no further details.
Jakarta-based security analyst Sidney Jones, who heads think-tank the Institute for Policy Analysis of Conflict, described the claim by the jihadists as "very credible" and that JAD's Bandung branch was behind the assault.
Al Chaidar, a terrorism expert from the University of Malikussaleh in Indonesia's Aceh province, said he also thought the claim credible.
"I think it is credible because they've already said on (messaging service) Telegram that they are happy about the bombing -- they are just reiterating it on Amaq," he said.
Police say bombs used in Wednesday's attacks were made from pressure cookers, similar to a device used in an attack by a JAD militant in Bandung in February.
In that assault, police shot dead the attacker after he allegedly set off a small bomb in a park and then stormed a local government office. No one else was hurt.
JAD was designated a terrorist organisation by the United States in January, which said the network was an umbrella group for about two dozen extremist outfits.
Some have pointed the finger at the group for carrying out last year's Jakarta attack.
