FOR decades, South-East Asia has had two lucky bulwarks against militant Islam: the peaceful, tolerant form of their faith practised by most South-East Asian Muslims; and the relative incompetence of local jihadists. But South-East Asia’s tradition of syncretic Islam has been threatened by stricter forms imported from the Middle East, seen as more modern and correct. Violent jihadism seems to be following the same pattern, if the bloody violence in central Jakarta, Indonesia’s capital, on January 14th, is anything to go by.

Four civilians and four terrorists died in the bombing of a Starbucks and a traffic-police post, and a long shoot-out with the police, that day. Authorities believe that an Indonesian, Bahrun Naim, planned the attack from Syria. He heads a South-East Asian unit fighting with Islamic State (IS) in Syria and Iraq. Governments in the region have long feared something like this.

Indonesian police have since arrested at least 13 suspected terrorists, and killed another. In Malaysia the police arrested a man suspected of planning to blow himself up at a bar, and three other Malaysians were sent back by Turkey after allegedly trying to cross into Syria to join IS. This week Singapore said that late last year it arrested and prepared to repatriate 27 Bangladeshi construction workers suspected of plotting terrorism back home.

Beyond this flurry of activity lie deeper questions about how to respond to the threat. Islamists have long been active in South-East Asia. Members of Jemaah Islamiya (JI), dedicated to establishing a South-East Asian caliphate, were behind the bombing in 2002 of a Bali nightclub that killed more than 200. They are suspected of other bombings of western targets in Indonesia and the Philippines.

After the Bali bombing the Indonesian police created Detachment 88, an elite counter-terror squad financed and trained by America and Australia. It killed or captured much of JI’s leadership. The Philippines, Malaysia and Thailand also arrested JI higher-ups. The group is weakened.

But the threat never entirely receded. And some now fear that IS could establish a base in South-East Asia. The region offers plenty of remote areas outside state control in which militants can hide. Both the Philippine island of Mindanao and southern Thailand have endured long-running insurgencies waged by Muslim minorities.

Just as veterans who fought the Soviets in Afghanistan boosted regional jihadist capacity in the early 1990s, many worry that returning fighters from Syria will do the same today. The Soufan Group, a security consultancy, estimated in a December report that at least 600 South-East Asians had gone to fight with IS. It is unclear how many have returned. The report says 162 people (including women and children) have returned to Indonesia from IS territory. Sidney Jones, who runs the Institute for Policy Analysis and Conflict in Jakarta, believes that the number of trained fighters who have returned is much lower. Some are in custody, but Peter Chalk of the RAND Corporation, an American think-tank, says the Indonesian authorities lack “a good feel about how many have returned…and what they’re doing in terms of radicalising populations.”

Of course, IS has also proved adroit at radicalising from afar. Thousands of Indonesians have publicly pledged allegiance to the group, and Mr Naim appears to have found local jihadists to carry out the attacks. At least one was said to have been radicalised, like many others, in an Indonesian prison. Ms Jones says Mr Naim used encrypted messages on social media in an effort to inspire attacks in Malaysia. Singapore’s home-affairs minister, K. Shanmugam, warned this week that “It is not a question of ‘if’, but ‘when’,” Singapore will suffer a terrorist attack. He said the government would roll out new measures “covering both the hard and soft aspects of Singapore’s security”.

Counter-terrorism strategies that worked before may prove less effective against transnational entities such as IS, which inspire online self-radicalisation and lone-wolf attacks. In Indonesia supporting or joining IS is not illegal, though the government is mulling broader counter-terrorism laws with powers of preventive detention. The country’s two biggest Muslim social movements—Muhammadiyah and Nahdlatul Ulama—have been trying to counter jihadist propaganda.

In Malaysia, however, the government itself has thoroughly politicised Islam, leaving little room for dissent from its harshest rules. A study last year found more than 70% of Malaysia’s ethnic-Malay, Muslim, majority support hudud laws such as stoning for adultery. Another found that 11% of Malays viewed IS favourably.