According to the Ministry of Home Affairs (MHA) of Singapore, the two cases involved were Kuthubdeen Haja Najumudeen, 36; and Suderman Samikin, 47, who were said to support the IS or make plans to join Muslim jihadists.
The Ministry said these were detained in two separate cases under the ISA, which allows detention for up to two years without trial.
It noted that investigations have determined that these men have become extremist and harboured their intention to go to Syria for joining the self-claimed IS group in Iraq and Syria.
Singaporean leaders warned that the country was a main target for an attack, as it was considered the region's financial centre.
