Separiano, alias Mambo, said he learned how to make bombs on the Internet – and bought material to do so with money donated at an Islamic study group, or Majelis Taklim.

Mambo was a deputy leader of Majelis Taklim in Tanah Abang, he told a Jakarta court on November 18th, during his trial as a suspect in a May 2013 plot to bomb the embassy of Burma.

He bought explosive materials in small quantities "to prevent any suspicion," The Jakarta Post quoted him as saying. And he used the taklim sessions as a way to connect with other radicals.

His case underlines to authorities some of the ways individuals inclined to militancy find one another, reinforce their misguided beliefs, raise money and plot their actions.

"Taklim is one of the sources of recruiting," terrorism expert Noor Huda Ismail told Khabar Southeast Asia. It is one of four ways terrorists strengthen their networks, he said.

"First, and maybe this is the most common, they are regrouping through internet forums including social networks," he said. "Marriages among radical Muslims are considered another way.

"Third, religious teachings or taklim; [fourth], prisons and visitations in prisons," he explained.

On screens and behind bars

Via social media, Mambo found others who wanted to "help" Burma's Rohingya Muslims by committing acts of terrorism. Among them, according to prosecutors, was Sigit Indrajit, a 23-year-old herbal product seller and member of Islamic State of Indonesia (NII).

"Sigit was connected to Separiano through Facebook," terrorism expert Wawan Purwanto said.

"Funding, connections and attacks are the three components of terrorism in Indonesia," he said.

The connections are also made in prison. Terrorists or radicals often return to their groups or engage in retaliatory attacks after serving several years in prison, he said.

"Recruitment and radicalism in prison is something that our authorities can address," Wawan said.

Militancy and marriage

Marriage among radicals or terrorists is also a strategy for strengthening militant organisations.

The sister of former Jemaah Islamiyah (JI) commander Nasir Abas was married to one of three main Bali bombers, Ali Gufron. Udin, a JI member in Medan, married the widow of one of the CIMB Niagara robbers.

But limiting regrouping through marriage is a major challenge, according to Yudha Pramudia, a University of Indonesia graduate student in security studies.

"Many radicals use marriages to strengthen their organizations. Marriages can also contribute to building cross-country and cross-region relations among radicalism," he said.

"The problem is stopping the marriages, even if the police are aware of the motives. It is very personal; the state and religion will not oppose it."

The true nature of Islam

Tangerang, West Java cleric Fakhrudin Rahmat agreed that curbing terrorist regrouping through taklim, marriage, and the internet is difficult.

"Our region is relatively close to the capital, Jakarta. Many radicals benefit from the access to technology, which has allowed them to assemble bombs and to reconnect with their groups or other groups. West Java is also popular with Muslims for religious taklim," he told Khabar.

"Muslim leaders must be aware of the possibility that taklim is conducted by radicals. This is the hardest part; taklim and marriages are untouchable by the government."

Youth need to be embraced by their community, and educated about the true nature of Islam, he added.

"We only can see any behavior change when they are close to us. Therefore, education in school, through family, and in the neighborhood is important. It will help our youth to understand why terrorism and jihad by killing others is wrong in Islam," he said.