Suicide bombers suspected to be from an Islamic State-inspired group killed at least 11 people and wounded 40 in attacks on Christians attending Sunday morning services at three churches in Indonesia's second-largest city of Surabaya, officials said.
Indonesia, the world's largest Muslim-majority country, has seen a recent resurgence in homegrown militancy inspired in part by Islamic State.
East Java police spokesman Frans Barung Mangera said explosions took place in three churches and at least 11 had died and 40 had been taken to hospital. He called on people to remain calm.
"All places where the public can gather, security has been tightened in those places," he told a news conference.
Earlier, he told Reuters that an unexploded device at one location had been "secured".
Television footage showed one church where the yard in front appeared engulfed in fire, with thick, black smoke billowing up. A large blast was heard hours after the attacks, which Mangera said was a bomb disposal squad dealing with a device.
There was no immediate claim of responsibility for the attacks.
Wawan Purwanto, communication director at Indonesia's intelligence agency said Islamic State-inspired group Jemaah Ansharut Daulah (JAD) was believed to be behind the bombings.
JAD is an umbrella organization on a U.S. State Department "terrorist" list that is estimated to have drawn hundreds of Islamic State sympathizers in Indonesia.
The attacks come days after militant Islamist prisoners killed five members of an elite counter-terrorism force during a 36-hour standoff at a high security jail on the outskirts of the capital, Jakarta.
The church attacks were likely linked to the prison hostage standoff, Purwanto said.
"The main target is still security authorities, but we can say that there are alternative (targets) if the main targets are blocked," he said.
SUICIDE ATTACK USED MOTORBIKE
At St Mary's catholic church, the first place of worship to be attacked, the bombing happened after an earlier mass was over and when the church was getting ready to hold another service.
Inspector general Machfud Arifin told CNN Indonesia the suicide attack at St Mary's was carried out using a motorbike.
A witness interviewed by CNN Indonesia said shortly before the explosion he saw a person on a motorbike drive in carrying a cardboard box.
Separately, an internal police report reviewed by Reuters said a suspected bomb exploded in a car in the parking lot of a Pentacostal church, setting alight dozens of motorbikes.
In the third location, the Indonesian Christian Church, two veiled women entered the church's yard where they were stopped by a security guard before an explosion occurred at the same spot, according to the police report.
Television images showed toppled and burnt motorcycles and debris scattered around the entrance of one church and police cordoning off areas as crowds gathered.
President Joko Widodo was due to visit the wounded in Surabaya on Sunday, police said, while Indonesia's Foreign Minister Retno Masudi condemned the attacks.
"We will not back down in the fight against terrorism," Marsudi said in a message sent on Twitter.
A spokesman for Indonesia's church association (PGI) called on the government for more help on security at churches.
"PGI is concerned because this had happened many times and often taken place around the time of Sunday services," said Jeirry Sumampow, a spokesman for the Indonesia's Communion of Churches.
Nearly 90 percent of Indonesians are Muslim, but the country is also home to sizeable communities of Hindus, Christians, Buddhists, and people who adhere to traditional beliefs.
Indonesia has had some major successes tackling militancy inspired by al Qaeda's attacks on the United States in 2001. But there has been a resurgence of Islamist activity in recent years, some of it linked to the rise of Islamic State.
The most serious incident was in January 2016 when four suicide bombers and gunmen attacked a shopping area in central Jakarta.
Churches have also been targeted previously, including near-simultaneous attacks on churches there at Christmas in 2000 that killed about 20 people.
