Indonesia began trials Monday of seven men on charges of conspiring with terrorists and recruiting for militant groups in the Mideast, including the Islamic State, which has an estimated hundreds of Indonesians as members.

The government has outlawed the Islamic State group and spoken forcefully against it, as have mainstream religious groups in the world's largest Muslim nation. One fear is that militants who travel abroad will return home and conduct terrorist acts in Indonesia.

The West Jakarta District Court began separate trials for Ahmad Junaedi, Ridwan Sungkar, Helmi Muhammad Alamudi and Abdul Hakim, as well as two others who helped them go to Syria to join Islamic State jihadists.

The seventh, Tuah Febriwansyah — also known as Fachry — is accused of actively spreading IS propaganda through his own radical website and posting violent videos of terrorism activities on the Internet, including a video showing militants in Syria giving military-style training to Indonesian children.

The seven men being tried, aged 32 to 51, were arrested in police raids in late March and early April in the capital, Jakarta, and East Java's Malang town.

State prosecutor Anita Dewayani told the court that Junaedi, Sungkar, Alamudi and Hakim attended jihadist training organized by IS in Syria, pledged allegiance to the group's leader Abu Bakar Al Baghdadi, and fought with the group for up to seven months.

"Islamic State in Syria and Iraq has been declared as a terrorist group by the United States and Indonesia," Dewayani said, "The defendants deliberately conspired with the group in Syria, spread hatred and even join in wars with them to revenge the deaths of Islamic fighters."

If found guilty, the seven defendants would face up to 20 years in prison under Indonesia's anti-terror law.

Indonesian authorities estimate over 600 Indonesians have joined the ISIS Daesh in Syria or Iraq.

For the first time since the 1990s and the Afghan jihad, Indonesians, Malaysians and other extremists in Southeast Asia are traveling abroad in an organized fashion to join a global militant movement, picking up battlefield skills and militant contacts.

Security officials fear they could take part in terrorism on their return to Southeast Asia, as those trained in Afghanistan did in attacks such as the 2002 Bali bombings, which killed 202 people. Radicals at home also could heed the Islamic State group's exhortations to carry out revenge attacks on Western targets.

In response to the threat posed by foreign fighters, the U.N. Security Council last year adopted a resolution demanding member states prevent the recruitment and travel of people to join militant organizations like the Islamic State group.

After the charges against the seven defendants were read, the panel of three judges adjourned the trial until next Tuesday.

The trial of another suspect, Muhammad Amin Mude, started last week, and five more are due to begin in coming weeks.