Three Austrian teenagers were given custodial terms Thursday (October 13th) for trying to join the "Islamic State of Iraq and the Levant" (ISIL) in Syria, AFP reported.

The trio, one aged 16 and two aged 15, who were not named, pleaded guilty to participation in a "terrorist" organisation at a trial conducted behind closed doors in Vienna.

Bulgarian authorities arrested the 16-year-old in May on his way to Syria to join ISIL, sending him back to Austria where he was put in custody but then released.

He then attempted to convince 10- and 11-year-olds to join the extremist group. He was given a 10-month sentence plus a further 20 months suspended.

The other two had concrete plans to go to Syria but were prevented from leaving in June, prosecutors said. One of them attacked his father with a screwdriver after he refused to give his son his passport.

He was also given a 10-month term and 20 months suspended and the other 15-year-old was sentenced to seven months with 14 months suspended.

All three, who were of Chechen and Turkish origin, had been radicalised in just a few months, the court heard.

Like other European countries, Austria has seen a wave of people -- 260, according to the government -- leave the country to join ISIL in Syria and Iraq.

Some have since returned. Around 40 of these are in custody and more than 80 are under close surveillance, according to the interior ministry.