As per media reports, two people were killed at the Santa Maria Church in the Ngagel Madya area of Indonesia's second-largest and busiest city, one other succumbed to injuries at the Surabaya Centre Pentecostal Church and two others were killed at the GKI Diponegoro Church.
Members of police bomb squad inspect wreckage of motorcycles at the site where an explosion went off outside a church in Surabaya, East Java, Indonesia.
The first explosion took place at 7.15 am (Jakarta time) and was followed by others with the interval time of about five minutes, according to the police.
Police have only given details of one attack on Santa Maria Catholic Church. The third attack occurred at the city's Pantekosta Church, during which another 2 people died.
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With more than 260 million people, Indonesia is the world's most populous Muslim-majority country. The Jemaat Ansharud Daulah (JAD) planned to carry out attacks on police but switched to target churches, an agency spokesman told Metro TV. Inspector general Machfud Arifin told CNN Indonesia the suicide attack at St Mary's was carried out using a motorbike.
Indonesia has had some major successes tackling militancy inspired by al Qaeda's attacks on the United States in 2001.
He added that the bombings were likely to be linked to an incident earlier this month, when five members of the security forces were killed during a 36-hour standoff with militant Islamist prisoners at a high security prison on the outskirts of the capital Jakarta. In recent years, the country has faced a new threat as the rise of IS in the Middle East invigorated local militant networks.
Churches have also been targeted previously, including near-simultaneous attacks on churches there at Christmas in 2000 that killed about 20 people.