IS said it was also responsible for ordering that attack.
Police in Indonesia say the latest bombings in Surabaya may have been motivated by last week's clashes at a high-security detention center where members of a local militant organization are being held.
How was JAD involved in the Surabaya attacks?
Indonesia's deadliest terrorist attack occurred in 2002, when bombs exploded on the tourist island of Bali, killing 202 people in one night, mostly foreigners.
A second is the attackers, who appropriate the name of a worthy and long-established faith that espouses tolerance, justice and civil harmony, have about as much to do with Islam as the Klu Klux Klan has to do with Methodism, the Roman Catholic Church or Anglicanism.
In one attack, a family forced their eight-year-old daughter to launch a suicide bombing on Surabaya's police headquarters, according to police.
At Surabaya Centre Pentecostal Church, Futrianto then drove his auto onto the church grounds and detonated explosives.
The attack on Surabaya's police headquarters came a day after another family, including four children, detonated bombs that targeted three churches leaving 12 people dead and at least 40 injured. Four of the bombers died.More news: Italy's new government makes economic promises
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Tito added that unlike any other explosives, TATP did not need a detonator to set the bomb off. "Heat or a mere shaking motion can cause the bomb to explode".
What is the connection to IS?
The Islamic State (known as IS) claimed responsibility for the church attacks.
National police spokesman Brigadier General Muhammad Iqbal confirmed that the unit of the flats was inhabited by an alleged terrorist with family members.
What kind of explosives did they use?
Abdurrahman, however, has recruited militants to join IS, is thought to have been in communication with leaders of the jihadist group, and is the main translator for IS propaganda in Indonesia, according to analysts and authorities.
Nearly immediately afterwards, there were explosions in a protestant church on the Diponegoro street, where two people were killed, and another one at a pentecostal church on Arjuno street, where another two people died.
The East Java Police have found a connection between the church bombings and Sidoarjo bombing.