Six suspected militants were rounded up on Friday in dawn raids on Batam island, about 15 km (10 miles) south of Singapore, where police believe the men planned to fire the rockets from.
Authorities identified the leader of the group arrested on Batam as Gigih Rahmat Dewa, who local media said was a 31-year-old factory worker from the Javanese city of Solo. Solo has been linked to several previous attacks by Islamist militants in Indonesia.
The group was suspected of having direct links to Bahrun Naim, an Indonesian who had lived in Solo but is now believed to be fighting with Islamic State in Syria.
“The six people led by GRD had planned to launch attacks,” National Police Chief Tito Karnavian told reporters, referring to Dewa by his initials. “They were in direct contact with Bahrun Naim in Syria and he had ordered them to attack Singapore and Batam.”
Indonesian investigators believe that Naim was one of the masterminds behind an attack in January in the Indonesian capital, Jakarta, in which eight people were killed, including the four attackers.
Singapore’s home affairs minister, K. Shanmugam, said the men had plans to hit Marina Bay, the state’s glittering downtown waterfront, where night-time Formula One Grand Prix Races are held alongside a giant ferris wheel and a swanky casino resort.
“This shows how our enemies are thinking of different ways of attacking us,” Shanmugam said in a Facebook posting.
“Terrorists … will seek to come in through our checkpoints; they will also try to launch attacks from just outside. And this is in addition to lone wolf attacks from radicalized individuals/groups. We have to be extra vigilant.”
Prime Minister Lee Hsien Loong said this week Singapore was a target for Islamic State because it is “a rational, open, cosmopolitan country” even though it is not involved in the U.S.-led campaign against the group in the Middle East.
Some security analysts were doubtful that a rocket attack on Singapore from Batam was feasible, but Tim Ripley of Jane’s Defence Weekly said it was possible.
“They would be the long-range variants of the Grad rocket -originally from Russia but copied in China, Iran, Pakistan and several other countries,” Ripley said. “Very simple to use but very inaccurate at the ranges for this attack. The damage would depend on where they hit but the potential for casualties would be high.”
If the plan for a rocket launch on Singapore is confirmed, it would suggest that militants in Southeast Asia are preparing far more sophisticated attacks than those of recent months.