Jakarta: Singapore has deported four Indonesian men thought to be followers of a leading Islamic extremist as they allegedly tried to travel to Syria, police said Tuesday.
The four, who included a 15-year-old boy, were arrested Sunday in the city-state when immigration officials became suspicious after checking their documents, and finding one of them had previously spent time in Syria.
Authorities deported them to Batam, an Indonesian island not far from Singapore, the same day, and they have since been sent on to Jakarta.
After questioning the men, Indonesian officials "suspected that these four Indonesians were heading to Syria", police spokesman Agus Rianto told AFP.
"We are now investigating the case to find out more."
National police chief Badrodin Haiti said the group were thought to be followers of radical preacher Aman Abdurrahman, who is in jail for his role in forming a militant training camp, and has pledged allegiance to the Islamic State (IS) group.
There have been suspicions Abdurrahman may have helped plan last month`s gun and suicide attacks in Jakarta that left four attackers and four civilians dead.
They were claimed by IS and were the first major attack in Indonesia for seven years.
Police refused to be drawn on whether the detained men, all from the main island of Java, had been trying to join IS, which controls vast swathes of territory in Syria and Iraq.
They originally entered Singapore from Batam but left for Malaysia, where they stayed only several hours, said local police chief Helmy Santika.
They were detained as they came back into Singapore, where they planned to catch flights, he added, without giving further details.
Singaporean authorities did not immediately comment.
Indonesian police have launched a nationwide crackdown since the Jakarta attacks, rounding up dozens of alleged Islamic extremists.
Indonesia, the world`s most populous Muslim-majority country, suffered several major bomb attacks by Islamic radicals between 2000 and 2009, but a subsequent crackdown weakened the most dangerous networks.
However, IS has provided a potent new rallying cry for Indonesian extremists, with hundreds believed to have headed to fight in the Middle East with the jihadists.