Hitting Singapore from Batam would have required a military- grade rocket and complex calculations, said a military observer.
Though it is not known what kind of rockets the suspects planned to use, weapons and equipment editor Kelvin Wong of military publication IHS Jane's told The Straits Times they would likely have needed a military-grade rocket able to travel the distance of around 25km between the Indonesian island and Singapore. If they were building their own rocket, fine calculations would have been required.
"Building a rocket requires a high level of physics," he said. "There are also quite a lot of variables they need to account for - like wind direction, the launch angle, how much propellant to put in the rocket."
Given the distance to Singapore, the suspects would also have needed rockets more powerful than the homemade Qassam ones fired by Hamas and Palestinian militants at Israel which have a maximum range of about 12km.
Reaching Singapore from Batam would require more powerful weaponry such as Katyusha-style, Grad and Chinese WS-1E rockets.
Batam's terror links
Dwi Djoko Wiwoho, director of the Indonesia Investment Coordinating Board's licensing office in the Riau Islands, and his wife leave their house in Batam to join the Islamic State in Iraq and Syria (ISIS).
He was to return to work from leave on Sept 1.
Four Indonesian followers of radical ideologue Aman Abdurrahman are deported from Singapore.
They had planned to use Batam and Bintan islands as transit points for others heading to the Middle East to join ISIS.
July 12, 2016
Indonesian police lower the terror alert levels in the Riau Islands after raising it following a bomb threat the previous week. A little-known militant group, Kelompok Islam Insaf, had sent two letters by local mail to the Singapore offices of ferry operators Horizon Fast Ferry and Batam Fast on July 4, threatening to strike tourist destinations such as Tanjung Pinang, Nagoya Hill mall in Batam, and key ports in Batam and Bintan.
Indonesian intelligence is alerted that several Uighurs, a Turkic-Muslim ethnic group in China's western region of Xinjiang, have entered the Riau Islands province. Uighur militants have been known to link up with extremist groups in Indonesia.
Aug 5, 2016 Indonesian police arrest six suspected militants in Batam.
The purported leader of the cell had plans to use a rocket to attack Marina Bay.
But S. Rajaratnam School of International Studies research fellow Wu Shang-su highlighted the possibility of attackers launching a rocket from a boat nearer to Singapore, possibly putting Marina Bay within range.