The issuing of a Restriction Order under the Internal Security Act (ISA) against a formerly accredited religious teacher shows the Government's readiness to act against anyone who threatens society, said Home Affairs and Law Minister K. Shanmugam.
He added that all Singaporeans can promote their religion as long as it does not promote violence or put down other races or faiths.
"We have been very strict about it; we have said across all religions, promote your religion, but you cannot promote violence, you cannot run down another religion, you cannot run down another race," he said.
"The vast majority of our people as well as religious leaders understand that, which is why Singapore is the oasis of racial and religious harmony that it is when compared with many parts of the world."
Mr Shanmugam was speaking to reporters yesterday after his ministry issued a statement that a former religious teacher and his student who held radical beliefs that promote violence and views detrimental to Singapore's cohesion have each been issued a Restriction Order (RO) under the ISA.
The Home Affairs Ministry said Murad Mohd Said, 46, a freelance religious teacher who was issued an RO on Dec 5 last year, was struck off the Asatizah Recognition Scheme (ARS) last May for his segregationist ideologies that contravened the ARS Code of Ethics.
The ministry said Murad taught that it was compulsory to kill apostates, whom he defined broadly as non-believers of Islam, people who renounced the religion as well as Sufis and Shi'ites, both of whom are minority groups in the community.
He also taught his students that Muslims were allowed to defend themselves by waging "armed jihad" against "infidels who persecuted them", and encouraged his students to withdraw from Singapore's secular society, disregard secular laws and adhere to syariah law, the ministry added.
Murad's student, 56-year-old technician Razali Abas, was arrested last September and placed on an RO in October to "prevent him from continuing his downward spiral into extremism". He held radical views on using armed violence against the perceived enemies of Islam, the ministry said.
Asked why Murad was not placed on an RO or a Detention Order when he was struck off the ARS last May, Mr Shanmugam said the Internal Security Department makes a "careful assessment of people" before taking action.
Often, he said, officers would try to engage those who might be veering off the accepted path and advise them about the law.
"Only if all of that doesn't work and you continue - as in his case - to advocate violence and killing of others... then we will act," he said.
The minister commended the agencies for striking Murad off the ARS when they found out that his teachings were "not appropriate".
The ministry also said in an update that the RO issued against Singaporean Jauhari Abdullah was allowed to lapse on Sept 14 last year.
He was a senior member of terror cell Jemaah Islamiah and was detained in September 2002 and released in September 2012, before being placed on an RO.
