Two self-radicalised Singaporeans were detained under the Internal Security Act (ISA) last month over links to terrorism-related activities, the Ministry of Home Affairs (MHA) announced today.

MHA said investigations revealed the duo, aged 29 and 18, had harboured an intention to make their way to Syria to join the terrorist group, Islamic State in Iraq and Syria (ISIS) and engage in violence there.

The 29-year-old is a self-radicalised individual influenced by ISIS' online radical propaganda.

In May, he was convicted and sentenced to three months' jail for inciting religious violence through his pro-ISIS postings on social media.

As he continued to express unstinting support for ISIS throughout his three-month imprisonment, he was arrested under the ISA in July for investigations to assess if he posed a threat to Singapore's security.

Subsequent investigations showed that the individual planned to travel to Syria to join ISIS, once he had raised sufficient money to fund the trip.

He had also decided that if he was unable to join ISIS, he would consider fighting alongside a regional militant group that he considered to be aligned with ISIS.

He was undeterred by his arrest under the ISA and said he would pursue his plans to join ISIS after his release from detention, adding he was prepared to die in the course of defending the 'caliphate' that was declared by ISIS.

The 18-year-old was radicalised by online radical propaganda put up by ISIS to the extent he harboured the intention to carry out armed jihad for ISIS.

He was prepared to be trained by ISIS to fight and kill the group's enemies, and die in the process so that he would receive divine rewards for dying as a martyr.

MHA said the detentions of the duo underlined the persistent ISIS threat and the threat posed by self-radicalised Singaporeans.

A few of the Singaporeans who have been detained had even been prepared to carry out terrorist attacks in Singapore.