SINGAPORE - The eight Bangladeshi men detained under the Internal Security Act (ISA) late last month for plotting terror attacks back in their own country had been working in Singapore for between three and 10 years, the Ministry of Home Affairs (MHA) said on Wednesday.

The men, who called their group Islamic State of Bangladesh (ISB), were not known to be radicalised or involved in terrorism-related activities when they came here to work, the ministry added.

But in the few months before they were picked up by the Internal Security Department in late March and April, ISB members met mainly in open parks or fields. They also shared large amounts of radical propaganda and videos which deepened the radicalism of members.

The group also had an organisation structure which had set out the specific roles of the leader, deputy leader and persons assigned responsibilities for tasks like finance.

The Bangladeshi authorities have been informed of the group and its activities, and have been helpful in providing some information, the ministry said.

MHA made these comments in additional remarks to the media today (May 4), a day after it announced the detentions of the eight, who were planning to stage attacks back home and had a target list, manuals for bomb-making, and had raised funds to buy firearms for attacks back home.

Home Affairs Minister K. Shanmugam said on Wednesday the latest arrests were a reminder of a wave of radicalisation sweeping through the world and this region.

"We could have been a target, because they were prepared to attack anywhere. If they had been directed to attack in Singapore, they would have attacked in Singapore. So it shows the seriousness," said Mr Shanmugam, adding that security agencies here had done well to identify these men and move in quickly.

Mr Shanmugam was speaking to the media on the sidelines of a closed-door forum on religious extremism at Temasek Polytechnic.

He also hit back at comments made by Singapore Democratic Party chief Chee Soon Juan, who had previously called for the Internal Security Act to be abolished, this morning.

Dr Chee on Wednesday sidestepped questions on the Act, but said the terror problem in Singapore was an immigration issue.

"I think this shows a lack of understanding of the nature of the problem," said Mr Shanmugam, pointing out that hundreds have been arrested in the region for radicalisation, including Singaporeans in Singapore.

"So what does Dr Chee suggest? That we say no to all foreign workers? Or we say no to all foreign workers who are Muslim? I think he should clarify," he said.

He pointed out that there were "tens of thousands of Bangladeshi workers" here who work in construction and as cleaners in the Town Councils.

"So what do we do? Send them all back? Who is going to do their jobs? And also in the construction sector, (if) you send them back, who suffers? Singaporeans will lose their jobs too," said Mr Shanmugam.

These matters, he added, "require careful consideration, proper thought and we should all just avoid taking cheap shots at political opportunism".

Meanwhile, MHA also said there was no indication that ISB members were also part of the earlier religious study group of 27 Bangladeshi men arrested last year, all of whom have been deported.

Some of them were, however, personally acquainted with a few members of that radical group because they chanced upon one another in Singapore.

The ISB is the first group comprising all foreigners to be detained under the ISA for terrorism-related activities in Singapore.

MHA also gave details of the group leader, Rahman Mizanur, 31.

Rahman was working as a draftsman in a local construction firm at the time of his arrest.

He had been working on-and-off in Singapore since 2007, and when he last came to Singapore in December 2015, the authorities had no information to suggest that he had radicalised views.

Investigations found that Rahman's radicalisation began around 2013, when he read radical material online. He became more radicalised after a Bangladeshi shared ISIS propaganda material with him when he was in Bangladesh in 2015.

MHA had said on Tuesday that Rahman began recruiting his fellow countrymen in January this year, and formed the group in March.

Today, it confirmed that the eight Bangladeshi nationals in detention were arrested between late March and early April. They were then issued with two-year Orders of Detention in late April.

The members generally lived in different accommodation, and were all employed in the local construction and marine industries, but there was no significant concentration in any particular company.

All eight are still under investigation for their activities in Singapore, the ministy said.

It added that at the time of the arrests, the funds raised were from members' own contributions, and they are not known to have acted on their plans to procure firearms yet.

"Several of them are liable to be prosecuted for terrorism financing. Investigations are still ongoing and we are not able to comment further on this matter," the ministry added.

MHA also identified the five other Bangladeshi nationals who were picked up in connection with the case, and said they were not involved in ISB but possessed or proliferated jihadi-related materials, or supported the use of armed violence in pursuit of a religious cause.

They are: Evan Galib Hassan Chowdhury, Rana Masud, Pailot Md Rana Miea, Islam Tanjemul and Alomgir Md.

MHA also said that following the arrest of the 27 Bangladeshi nationals last year, it has worked with the Ministry of Manpower and an advisory was sent to dormitory operators, asking them to engage the foreign workers living in their quarters.

"Efforts to reach out to and engage the foreign worker population in Singapore are on-going," it added.

"The uncovering of the ISB group in Singapore sends a strong signal that we cannot take our security for granted or be complacent. As part of ongoing heightened vigilance against the terrorism threat, Singapore has enhanced our law enforcement agencies' capabilities to prevent, detect and respond to terrorist attacks," MHA said.

"The Government also works closely together with foreign security services to share intelligence on terrorism activities, and with various religious and community groups to counter extremist ideology and protect our community from radical influences," it added.

With the latest case, there are currently 23 persons detained under the ISA for terrorism-related activities.