The leader of the al-Qaeda-linked Jemaah Islamiah (JI), the group behind the devastating Bali bombings, has been arrested in Indonesia along with one of the group’s expert bomb makers, a senior security source told This Week in Asia on Thursday. JI was behind all the deadliest terror attacks in Indonesia from 1998 to 2010 before it was weakened by Indonesian counterterrorism police, who arrested hundreds of its members during the period, including several leaders. But the network has been on the rise again lately, accumulating business interests in palm oil plantations as well as the mining industry to fuel its activities. The security source identified the leader as Ustad Arif, saying he had been arrested by Indonesian police about two months ago. In Indonesia, ‘call to jihad’ videos show threat of rising fundamentalism Arif, 54, hails from Klaten, Central Java, and has deep knowledge of Islam, the source said. “He is good at managing JI’s vast network and is highly respected by all members of JI,” said the source, who spoke on condition of anonymity because he was not authorised to speak to the media. Arif led JI for only eight months before he was arrested, the source said. He was the second JI leader to be arrested within the last two years. The security source said JI would “need time to find a figure” to take over leadership of the group. “In the meantime, JI will continue to operate. It is very strong but will still need to carry out consolidation as many of their leaders have been arrested,” the source said. JI terrorist leader’s arrest reveals thousands of recruits He said the Indonesian police counterterrorism squad, Detachment88, had never stopped monitoring or carrying out operations against JI all these years, despite its lower profile. Muhamad Taufiqurrohman, senior researcher at the Jakarta-based Centre for Radicalism and Deradicalisation Studies, said he expected that JI would now lie low until it selects a new leader. Arif’s predecessor, Para Wijayanto, was arrested in July last year and sentenced by a court to seven years’ imprisonment this year on terrorism charges as well as for sending JI members to Syria to fight alongside opposition rebels there. Following Wijayanto’s arrest, police discovered he had restructured and rebuilt JI into an organisation that had moved away from donations and robberies as its main source of income into an organisation with business interests in palm oil plantations and other commercial sectors. Under Wijayanto’s direction, JI’s palm oil plantations generated enough income to enable the group to pay its “officers” a monthly salary of 10 to 15 million rupiah (US$707 to US$1,061), according to police. Indonesian police also arrested JI’s expert bomb-maker, Upik Lawanga, two weeks ago, the source said. Lawanga had been on the country’s most-wanted list for 14 years. “Upik, alias ‘Professor’, was arrested with home-made pistols which he had made. He was the student of Dr Azahari Hussein,” said the source. Azahari, a Malaysian, made the bombs for the 2002 Bali attacks that killed 202 people, including 11 Hong Kong residents. He was killed in a shoot-out with police in East Java in 2005. He was known as one of the deadliest and most lethal bomb-makers in the region, and police have long worried that he had passed on his skills to his students. Included among those skills was the ability to assemble improvised explosive devices, said Ayob Khan Mydin Pitchay, the former counterterrorism chief of the Malaysian special branch, the intelligence arm of the Royal Malaysian Police. “While many JI members were trained to assemble an explosive device, the final process, including the circuit board, [was] produced by Dr Azahari ihimself,” said Ayob, who is currently police chief of Malaysia’s Johor state. Azahari was known to be extremely meticulous, surveying a target and its location before setting out to assemble bombs and ensure they could inflict “massive destruction”, said Ayob. “He was a genius – an idealist in making bombs that could explode with maximum force,” Ayob added. According to the source, Upik is also a skilled bomb-maker who assembled many of the bombs that were set off in Poso, Central Sulawesi, from 2005 to 2007. Among the terror attacks linked to Upik are the 2005 twin blasts at Tentena market in Central Sulawesi, which killed 22 people. Upik is alleged to have made the two bombs, said the source. After 2007, Upik maintained a low profile in order not to attract police attention, as JI wanted to preserve him for the long term. “JI has been hiding Upik meticulously and protecting him as he is a highly prized asset,” the source said.