by Zheng Shibo

JAKARTA, May 18 (Xinhua) -- Suicide bombings on Sunday and Monday in Indonesia's second-largest city Surabaya killed more than 20 people, while a police headquarters in Sumatra Island's Riau province was also attacked on Wednesday, with five people dead.

These attacks have made the passing week as a bloody one for the largest country in Southeast Asia.

The Surabaya attacks, which used children and women as suicide bombers, were linked to Indonesia's loosely organized Islamic State (IS) affiliates Jamaah Ansharut Daulah (JAD) and Jamaah Ansharut Tauhid (JAT), and the Wednesday attack was related to JAD, according to Indonesia's Police Chief Tito Karnavian.

The IS claimed responsibility for attacks in Surabaya and Riau, and police said the IS possibly instructed the Surabaya bombing and one of the suspects had been inspired by radicals returning from Syria.

The Indonesian government estimated that up to 700 Indonesians have joined the war in Syria and Iraq and some have traveled back.

Analysts said the returning IS fighters from war zones and Philippines' Marawi, are posing a growing new threat in Indonesia as they may become a source of ideological inspiration as well as bring operational know-how to poorly-organized and poorly-equipped local networks.

Tia Mariatul Kibtiah, an expert on the Middle East and Arabic studies in Indonesia's private Binus University, told Xinhua that since the IS is losing territory in the Middle East, the group may choose Indonesia, the country with world's largest Muslim population.

"As a result, the individual, lone wolf and small group IS-style attacks will be widely popular in the future terrorism development in Indonesia," she said.

The United Nations Security Council released a report earlier this year, which said the IS's losses in Iraq and Syria may intensify the threat to Southeast Asia, as funds and fighters disperse from the two war-torn countries.

Analysts said these IS-linked attacks also exposed the lingering threat from resurgence of homegrown militants group after the collapse of Jemaah Islamiyah (JI), which were convicted in relation to the 2002 Bali bombing.

Michael Hart, a researcher on terrorism in Southeast Asia, posted an article on news website Asia Sentinel, which said that in the years since (the collapse of JI), several newly-formed groups like JAD, JAT, Mujahidin Indonesia Timur (MIT) along with JI's offshoots have remained active beneath the radar, posing only a latent threat to the country.

In January 2016, four suicide bombers and gunmen from little-known JAD attacked a shopping area in the capital city of Jakarta, which killed eight people. JAD bombers also launched an attack at a bus station in East Jakarta in May 2017, killing the suspects and three police offices.

Indonesian police also blamed last week's deadly prison riot in Jakarta's outskirts of Depok, in which five policemen were killed by terror detainees, was instigated by JAD members.

Experts warned that JAD, who targets police, religious places instead of foreigners, embassies, hotels and nightclubs, may well become a more dangerous version of JI.

Mujahidin Indonesia Timur (MIT), a well-established group who has strongholds in rural regions, got international attention in October 2012 after its members shot down two policemen and killed three Mobile Brigade officers two month later. In addition, three civilians were killed by an MIT member in the beginning of 2015.

There have been only a few large-scale attacks in recent years due to a sustained and successful crackdown on militants following the 2002 Bali bombings that killed more than 200 people.

However, in 2017, Indonesian police's anti-terror unit apprehended 172 suspects, of whom 16 were shot dead during arrest attempts. The authorities linked the militants involved to either JAD, JAT or MIT.

Despite that the IS adds an extra dimension to the threat of Indonesia security, experts said the local political and religious dynamics are the central issues to cleaning up Indonesia's terrorism landscape.

Kibtiah told Xinhua that radicalism in Indonesia has been flourishing and pluralism and tolerance significantly reduced since 1998 which marked the fall of long-time former president Muhammad Suharto and the dawn of the reform era.

Radical groups began to advocate their mission of either implementing the Sharia law or establishing a caliphate. Extreme clerics attempt to influence ordinary Indonesians though sermons, according to Kibtiah.

Based on a Pew Research study in 2015, four percent of Indonesians, or around 10 million, have favorable opinions of militant groups. Analysts said since the Indonesian society has become more conservative in recent years, this support is bound to rise.

Indonesian President Joko Widodo is now demanding a revision of the 2003 Anti-Terrorism Law to give police more power to detain suspects pre-emptively and to prohibit Indonesians from joining overseas militant organizations.

Experts argued that given the prison riot by terror detainees last week, Indonesia's efforts at rehabilitating the homegrown militants are off target.

Kibtiah insisted that the government should intensify the international cooperation with Australia and other Western countries. Besides, the current Association of Southeast Asian Nations (ASEAN) security cooperation mechanism should be immediately utilized.

Indonesia's homegrown militants roughly posed a limited threat a decade after the Bali bombing under the country's intensive crackdown. However, as the infiltration of IS ideology to the region, Indonesia's terrorist movement has reached a critical point.

Evan A. Laksmana, A senior researcher at Indonesia think tank the Center for Strategic and International Studies, said in an article published on the Australian Strategic Policy Institute's website that Indonesia can and should do more to address the growing and increasingly lethal IS-linked threats.

"One should not rush into abandoning the current criminal justice model of counter terrorism in return for a more repressive, or 'war-fighting' one. As Indonesia's own long history tells us, repressive measures often lead to prolonged and more deadly conflicts in the future," he said.