With the emergence and growing influence of the Islamic State in Iraq and Syria (ISIS), the threat of transnational terrorism erupting in the region has grown significantly over the past year.

While ISIS and its affiliates threaten to destabilise the entire region, Singapore faces an outsized risk for a number of reasons, say experts.

They range from Singapore's reputation as one of the most secure countries in the world today, to its status as a global hub for finance and shipping, and its close relationships with the Western world.

The sum of these features puts Singapore in terrorists' sights, as any successful attack would be likely to shake global confidence in how secure people think they are.

"Although Indonesia and Malaysia oppose ISIS, Singapore is identified by the Southeast Asian terrorists as the region's closest ally of the United States," says Professor Rohan Gunaratna, who heads the International Centre for Political Violence and Terrorism Research (ICPVTR).

"Although Singapore's relations with the West and its hub status are its strengths, they also make Singapore a prized terrorist target."

Previously, the main terrorism risk in the region had been from militant group Jemaah Islamiah (JI). But it was dealt a major blow by strong security action in the decade following the September 11 attacks by Al-Qaeda, and following the discovery a month later of a plot by JI to bomb embassies in Singapore.

"Prior to ISIS' rise in June 2014, there was a sense that the physical threat was declining because of very effective security force action within Southeast Asia," says Associate Professor Kumar Ramakrishna, head of policy studies at the S. Rajaratnam School of International Studies (RSIS).

But ISIS has been a game-changer, serving as a rallying force for militant groups in South-east Asia, says Dr Kumar. Experts estimate that close to 30 groups from Indonesia, Malaysia and the Philippines have taken oaths of allegiance to ISIS over the past year.

"One of the reasons for this development is that despite all the actions by the coalition against ISIS in the Iraq and Syria region, they are still there, and appear to be very resilient," he says. "They (ISIS) seem to be consolidating, so this gives the impression that they are here to stay."

The support groups in Southeast Asia help translate and disseminate ISIS propaganda within the region - and are also a source of fighters for the conflict in Syria and Iraq.

To date, more than 700 fighters from Indonesia and 200 from Malaysia have made their way to participate in the violence in the region, a critical mass that prompted ISIS to form a dedicated South-east Asian military unit, Katibah Nusantara.

There is a real risk that these fighters could begin a fresh cycle of violence reminiscent of the JI threat after fighters returned from Afghanistan in the 1980s, says ICPVTR research analyst Jasminder Singh, who notes that a key Katibah leader is former JI member Bahrum Syah.

"While the Malay-speaking jihadists who fought in Afghanistan in the 1980s formed the backbone of the Jemaah lslamiah in the 1990s and the first decade of 2000, IS seems to have more grandiose plans for its Malay Archipelago fighters," he says.

A just-released paper co-authored by Singh traces the expansion of Katibah into three geographical groupings and the assistance it has provided to Indonesian terrorist groups, including its alleged funding of several foiled bomb plots in Indonesia.

The August issue of ISIS' online magazine Dabiq has also called for the targeting of embassies in countries that are part of the global coalition against the group - a coalition that includes Singapore, Malaysia and Indonesia.