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ISIS flagReuters

Two Norwegians accused of fighting with Islamic State (ISIS) extremists appeared before an Oslo court Tuesday charged with aiding a "terrorist organization", in Norway's first ever trial of suspected jihadists.

Djibril Bashir and Valon Avdylim -- of Somali and Albanian origin, respectively -- are accused of having fought with ISIS in Syria, according to the AFP news agency.

Avdylim was also charged along with his younger brother Visar with trying to send military equipment to another sibling who was killed in Syria in April 2014.

The trial marks the first time Norway has invoked a new provision under its criminal law allowing prosecution of any "economic or material support to a terrorist organization," an offence punishable by a maximum of six years in prison.

All three defendants have denied the charges, with 30-year-old Bashir admitting Tuesday he had joined ISIS in a non-fighting support role in 2013.

But he told the court he was “unaware” the organization had been labelled a terror group by the United Nations at the time.

"I noticed that many other insurgents were very corrupt in the way they handled civilians. Many of them set up checkpoints, kidnapped civilians, demanded money and stole," he said of his time in Syria.

Norwegian authorities feared that the two main defendants -- who returned to Norway in January last year -- would try to return to Syria or commit an attack on Norwegian soil.

The pair were arrest along with the younger Visar in May. The trial is expected to last for a month, according to AFP.

According to intelligence services quoted by the news agency, more than 70 Norwegians have travelled to join jihadist insurgents in Syria and Iraq.

In September, Norway arrested a group of extremists who planned to murder an entire family and film it as a "warning" to Western states intervening against ISIS in Iraq and Syria.

It is well-known that many foreign nationals have gone to Syria and Iraq to fight alongside ISIS, but exact data is uncertain. As of a year ago, estimates claimed that up to 75,000 foreign nationals had travelled to Syria.