Achmad Mohamed Hasan became the fifth man on death row in Indonesia for bombing western targets. At least 40 more are serving jail sentences of between three and 10 years. All are suspected members of the regional extremist group Jemaah Islamiah, which has links to the al-Qaeda terrorist network and is said to have helped train militants in the Philippines and Thailand.

British terrorism researcher Dominic Armstrong said that although there had not been an attack in Indonesia for a year, the threat had not lessened and Muslim militancy in the Philippines and Thailand was worsening.

Determining that Southeast Asia was 'certainly at the forefront of where the global threat lies', he said arrests, executions and government co-operation were having little effect. Officials needed to also tackle grass-roots problems that were driving people to extremism.

'At the heart of most terrorist issues - even of the more ideologically-driven ones - there are ultimately political gripes and it just requires the work to identify what it is that is bringing the foot soldiers in to support the fanatics,' Mr Armstrong, the director of research and intelligence for the London-based Aegis Defence Services, said. 'Appeasing local political issues can often be as simple as representation or employment opportunities that just give people something to live for rather than the cause.'

In Hong Kong for the CLSA Investors' Forum, where he spoke about the impact of terrorism on stock markets, he said only the top militants should be dealt with aggressively so as not to 'bring more and more people to the cause'.

Observers fear that is what has happened in Muslim-majority Indonesia. In separatist southern regions of Thailand and the Philippines, security forces are struggling against the increasingly sophisticated tactics of Islamic militants.

Military officials have expressed alarm at the advanced bomb-making skills of attackers, who appear to be sharing technology. Their bombs, which have claimed hundreds of lives in the past year, have used difficult-to-obtain chemicals and mobile telephones as timers so that devices can explode simultaneously in several locations.

Thai Islamists have increasingly adopted the methods of militants fighting US-led troops in Iraq, using what American soldiers there call 'improvised explosive devices' in roadside bombings, as well as beheading victims.

Concern has also been expressed about the increased profile of the southern Philippines group, Abu Sayyaf, previously known for banditry and kidnappings, but now considered a terrorist organisation following a series of high-profile bombings.

Jemaah Islamiah expert Zachary Abuza, who has spent much time researching Muslim extremism in the Philippines and Thailand this year, described the rise of the Abu Sayyaf as 'troubling'. He said the Philippines' government was not focused on the problem.

'The militants and the radicals still have to be arrested and dealt with. But the average foot soldier can be brought back into the fold through promises or development, amnesty and trying to get them to renounce their militancy and working with communities,' Dr Abuza said. 'All that is possible, but there are still people that are going to have to be dealt with through law enforcement.'