A plot to attack a bank and local police stations in East Java was foiled after five terror suspects were arrested during a series of raids by the elite Densus 88 counter-terrorism police on Wednesday.
Handwritten details of the plot were found on the suspects after they were nabbed at three separate locations across Blitar regency, said a local police chief on Thursday.
Blitar is about a three-hour drive from Surabaya, the capital of East Java, where three churches and the city police headquarters were hit by suicide bombers last month.
"We found a few notes, and on one of them was a plan to attack our police headquarters, a police post in Talun (sub-district), and a bank," said Blitar police chief Anissullah Ridha.
All five suspects have since been taken to the Surabaya police headquarters for further investigations, he added.
According to Antara state news agency, one of the suspects, a doctor identified only as NH, was armed with a gun and eight bullets.
He and two others, identified only as SZ and AN, were arrested in a rented house owned by fertiliser businessman Nanang, who goes by just one name.
NH had signed a three-year lease for the house, Talun sub-district chief Imam Harimiadi told Kompas news. He also said that the authorities visited some time ago and questioned him about the house and its mysterious tenant.
"But we didn't know what they did every day, because their door was closed," he added. "They had a gathering once, but it seemed very exclusive... you could not just go in."
Lieutenant-Colonel Anissullah said the latest arrests are part of efforts by the police to tighten security, following the suicide-bombings at the churches and the police headquarters in Surabaya on May 13 and 14.
They also come after the arrest of 37 suspects in connection with the Surabaya attacks which claimed 27 lives, including those of 13 perpetrators who are said to have been in sleeper cells with ties to the Jemaah Ansharut Daulah (JAD), a local terrorist group loyal to the Islamic State in Iraq and Syria (ISIS).
Among the suspects in custody is Syamsul Arifin, a 37-year-old resident from Blitar who was picked up with his wife by the police in Malang, East Java on May 16.
Syamsul, alias Abu Umar, is said to be the leader of a JAD terrorist cell in East Java and the police believe he had a hand in the Surabaya bombings, said Lieutenant-Colonel Anissullah.