Church engulfed in fire " There is one location where we can't enter yet", Mr Mangera said.
"In total 13 people are being treated at the hospital", East Java police spokesman added. On 19 July 2017 the Indonesian government had officially disbanded HTI in response to allegations that the group seeks to establish a caliphate in Indonesia.
Members of the bomb squad are also present at the spot.
The church attacks were likely linked to the prison hostage standoff, Mr Purwanto said. Another two died in a third attack at the city's Pantekosta Church, Mangera said.
Inspector general Machfud Arifin told CNN Indonesia that the suicide attacks were carried out using a motorbike at St Mary's church and a vehicle at another.
It is not known if there were casualties at the two churches apart from Santa Maria.
In a series of explosions in Christian churches in Indonesia killed 9 people, another 40 were injured.
Television footage appeared to show a person on a motorcycle driving into the grounds of a church before a bomb was detonated. "We will not back down in the fight against terrorism", Ms Marsudi said in a message sent on Twitter.
The police spokesman declined to give more details on the victims.
All three attacks occurred in Surabaya, Indonesia's second-largest city of around 2.8 million people in a country that holds the world's largest Muslim majority, Reuters reported.
Indonesia has had some major successes tackling militancy inspired by al Qaeda's attacks on the USA in 2001. In recent years, the country has faced a new threat as the rise of the Islamic State group in the Middle East invigorated local militant networks.
He said 41 people were wounded at that location, including two police officers, while one or more of the bombers were killed.
If in fact that was the mode of attack at one of the churches, it was apparently not one used at all the targets.
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