JAKARTA/SURABAYA • Indonesia's counter-terrorism squad Densus 88 has arrested terror suspects in East Java as well as Sumatra, including Medan and Riau, in the wake of deadly attacks this week.

North Sumatra police chief Paulus Waterpauw confirmed on Wednesday the arrests, including one in Tanjung Balai city on Tuesday, during which one suspect was shot dead and another injured while resisting arrest, the Jakarta Post reported.

Densus 88 personnel also arrested at least two other suspects in the provincial capital of Medan, the report said. They were identified as 28-year-old ojek or motorcycle taxi driver MYR, and 38-year-old milk seller SL. A suspect identified only as W reportedly fled.

Meanwhile national police chief Tito Karnavian said yesterday a total of eight alleged militants in Riau province had been nabbed by the anti-terror squad, reported Xinhua news agency. Police seized a flag of of the Islamic State in Iraq and Syria (ISIS) as well scores of weapons during the arrest.

In East Java, a total of 23 alleged militants were captured, according to police officers cited by Xinhua.

"We order the other alleged terrorists to surrender instead of being persistently hunted," said East Java's police chief, Inspector General Machfud Arifin. He added that four alleged terrorists were shot dead during the arrests.

Entire families of suicide bombers carried out attacks on three churches and at least two police headquarters earlier this week.

Around 30 people have been killed since Sunday in the attacks, including 13 of the suspected suicide bombers.

Police suspect the attacks were carried out by a cell of the ISIS-inspired Jemaah Ansharut Daulah, an umbrella organisation on a US State Department terrorist list that is reckoned to have drawn hundreds of Indonesian ISIS sympathisers.