Police carried out raids and made several arrests in Indonesia on Friday, as the country tried to find anyone who helped five terrorists carry out Thursday's deadly attack in downtown Jakarta. State police say they suspect an Indonesian man allied with ISIS planned the attack from Syria.

"Police raided several locations in the early hours of Friday morning" and made arrests in the Jakarta suburb of Depok, NPR's Anthony Kuhn reports. "Police found an Islamic State flag at the site of the arrests, but it's not clear exactly how they were linked to ISIS or yesterday's attacks."

According to Reuters, police killed one suspected militant and arrested two others.

Seven people died in Thursday's attack, which also left more than 20 people injured. Officials say five who died were the attackers, with two of them dying from suicide bombs and three others killed in gun battles with police.

In Jakarta, hundreds of people attended a rally and memorial for the victims of the attack, many of them carrying signs reading "We Are Not Afraid." They laid flowers and other offerings outside the Starbucks cafe that was at the center of the attack.

Police say they believe the attacks were plotted by Bahrun Naim, who the Jakarta Post says traveled to join ISIS in Syria after he served more than two years in prison for violating firearms laws. He had been arrested by the country's counterterrorism force.

According to Indonesia's national news agency Antara, two of the five attackers had previously served jail time on terrorism charges.

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