A former Singaporean detained under the Internal Security Act for terrorism-related activities was jailed for six weeks yesterday for flouting the Passports Act.

Zulfikar Mohamad Shariff had falsely declared that he had not obtained citizenship of another country when applying for a Singapore passport in 2013.

The 49-year-old, who was arrested for actively promoting terrorism and glorifying the terrorist group Islamic State in Iraq and Syria (ISIS), had acquired an Australian citizenship despite holding a Singapore citizenship.

Dual citizenship is not permitted in Singapore, and Zulfikar has since renounced his Singapore citizenship.

Zulfikar pleaded guilty to one charge under the Passports Act yesterday.

The court heard that Zulfikar, who lived in Australia for 14 years, had applied for Australian citizenship in 2011 with his then 15-year-old son, so that his child could evade his national service liabilities.

Zulfikar "took no steps to renounce" his Singapore citizenship when his application was successful, said Immigration and Checkpoints Authority Prosecuting Officer Assistant Superintendent (ASP) Ganeshvaran.

To prevent the local authorities from discovering his dual citizenship, Zulfikar would use different passports to travel to Singapore.

For example, he would depart from Australia to Malaysia using his Australian passport, and then travel to the Republic using his Singapore passport, said the prosecuting officer.

He successfully entered Singapore on 15 occasions without being detected, added ASP Ganeshvaran.

When it came to renewing his Singapore passport in 2013, he falsely declared that he "had not acquired the citizenship of another country".

Zulfikar was arrested by the Internal Security Department when he returned to Singapore in July 2016.

He had made many Facebook posts that promoted the terrorist group ISIS and its violent actions.

The Ministry of Home Affairs said Zulfikar's actions contributed to the radicalisation of at least two Singaporeans.

In mitigation, his defence counsel Lock Zhi Yong said that Zulfikar pleaded guilty at the first available opportunity and is remorseful.

He also suffered a "considerable loss of liberty" from being detained under the Internal Security Act for over four years.

Mr Lock said Zulfikar hopes to reunite with his wife and six children, aged between 10 and 24, in Australia.

However, the prosecuting officer said Zulfikar had "deliberately planned his travel route" to avoid detection by the authorities.

His sentence has been backdated to the date of his remand on Oct 8 this year.