The Australian embassy bombing underlines what terrorism experts have long warned - that hundreds of arrests have failed to neutralise the extremist group Jemaah Islamiah. Southeast Asia's top terrorism researchers believe more attacks will take place whenever the opportunity arises and that all cities are vulnerable. Analysts at the Institute of Defence and Strategic Studies in Singapore, Rohan Gunaratna and Andrew Tan Tian Huat, said they were not surprised by the car bombing. 'We were all expecting an attack,' said Dr Gunaratna, a former investigator with the United Nations' Terrorism Prevention Branch and chairman of the North Atlantic Treaty Organisation's working group on terrorism. He warned that preparedness must be maintained at the highest level throughout the region, but it was impossible to prevent attacks. 'This attack took place because the opportunity was there,' said Dr Gunaratna, the author of Inside Al-Qaeda: Global Network of Terror, a study of the international terrorist movement to which Jemaah Islamiah is closely linked. 'It wasn't because of the presidential election in Indonesia later this month or Australia's general elections next month - it was because the circumstances were opportune.' Dr Tan said Jemaah Islamiah's ability to carry out more attacks was indicated by the fact that of its estimated 3,000 members in Southeast Asia, between 500 and 1,000 were believed to have trained to make or plant explosives. Only 200 of its members had been arrested since the September 11 attacks. 'The embassy attack was no surprise,' Dr Tan contended. 'There have been a number of indications of Jemaah Islamiah's capabilities since the Bali bombings - the JW Marriott hotel bombing in Jakarta in August last year and the big arms haul uncovered a few months before in the town of Semarang.' He had no doubt that the terrorist group had its sights on other targets, such as Singapore. The city state's Deputy Prime Minister Tony Tan Keng Yam admitted last month when launching a national security strategy that an attack on Singapore was only a matter of time. Jemaah Islamiah's ultimate goal is to forge a giant Islamic state from Indonesia, Brunei, Malaysia, Singapore and the southern Philippines. It uses terrorist attacks in an attempt to destabilise regional governments and foster hatred. International Crisis Group's Indonesia project director Sidney Jones said the bombing was unlikely to have been intended to influence Indonesia's presidential election on September 20. But she believed it could become an issue as President Megawati Sukarnoputri and Susilo Bambang Yudhoyono made their final campaign rounds. 'The Indonesian public hasn't been interested in terrorism as an issue, so it's only occasionally been mentioned in the candidates' speeches,' Ms Jones said in Singapore. 'This attack increases the dislike and contempt for terrorist groups among Indonesia's public.'