JAKARTA (AFP) - Seven Indonesian men went on trial Monday accused of links to the Islamic State in Iraq and Syria (ISIS) group, and could face the death penalty if found guilty of breaking anti-terror laws.

They were all charged with being part of an "evil conspiracy" and accused of a range of crimes, from trying to aid acts of terror to supporting ISIS, which has been banned in the world's most populous Muslim-majority country since October last year.

Three of the accused - Ahmad Junaedi alias Abu Salman, Ridwan Sungkar alias Abu Bilal, and Helmi Muhamad Alamudi alias Abu Royan - allegedly went to Syria to join ISIS last year and received military training, prosecutors said.

"Not only has the defendant declared that he joined ISIS, he also joined military training in ISIS camps," prosecutor Teddy Irawan told a Jakarta court, opening the case against Sungkar.

"The defendant was aware that the objective of the training was preparation to launch acts of terror," he added.

One defendant, Tuah Febriwansyah alias Muhammad Fachry, was accused of running websites with pro-ISIS content, uploading articles such as one named: "Pledging loyalty to ISIS, why not?".

All the defendants were being tried separately.

The lawyer for six of the defendants, Asludin Hatjani, said he hoped his clients could escape the ISIS-linked charges as most of their crimes were alleged to have taken place before Indonesia banned the group.

Hundreds of Indonesians are feared to have travelled to the Middle East to join ISIS, which controls vast swathes of territory in Syria and Iraq. Several have been detained on their return.

However, counter-terror officials complain that current laws are still too weak to stop extremists leaving for Syria and to block the spread of radical information on the Internet.