Indonesian authorities arrested six suspected militants on Batam island on Friday who were believed to be linked to the Islamic State group and plotting an attack on nearby Singapore, a police spokesman said. Singapore said it had stepped up security in response. Indonesian police spokesman Agus Rianto told reporters the suspects had been plotting with a member of the Islamic State militant group in Syria to attack the wealthy city-state via Batam, which is about 15 km (10 miles) to the south. “What we understand so far is that they were planning to attack vital objects, busy areas including police offices,” Rianto said. The six arrested were suspected of having links to Bahrun Naim, an Indonesian fighting with Islamic State in Syria, police said. Indonesian investigators believe that Naim was one of the masterminds behind an attack in January in the Indonesian capital of Jakarta, in which eight people were killed including the four attackers. “There’s a link to Bahrun Naim because there was communication with Bahrun Naim – but whether they were affiliated with Bahrun Naim’s group or not – this is what we’re investigating now,” Rianto said. The Batam Pos newspaper quoted police as saying the six suspects were mostly factory workers aged between 19 and 46. Some media reported that the suspects had been plotting a rocket attack on Singapore, but that was not confirmed by Indonesian authorities. National police spokesman Martinu Sitompul said police and an anti-terrorist unit were in the early stages of their investigation….