Now aged 27 and 31, the pair were convicted of being members of IS, listed as a terror group in Norway and the West.

The oldest sister was sentenced to serve four years behind bars, while her younger sibling received a two-year sentence, with one of the years suspended.

The sentences were in line with what prosecutors had requested.

"The court found that it has been proven beyond a reasonable doubt that the two accused were members of IS, as much as women could and were supposed to be, as wives and housewives," the Oslo district court ruled.

The sisters, who are Norwegian citizens of Somali origin, had pleaded not guilty, insisting they had been forced to join the group and stay in Syria.

They secretly fled Norway in late 2013, aged 16 and 19, in order to -- as they later explained in an email -- take part in the fight against the regime of Bashar al-Assad.

Once in Syria, they married IS fighters. The eldest went on to have two daughters, while the youngest gave birth to one daughter.

Norwegian authorities repatriated the sisters in March 2023, citing the welfare of their children who were held with their mothers in the Kurdish-run Roj detention camp for jihadist prisoners in northeastern Syria.

In Norway, the identities of the accused are rarely disclosed publicly until the verdict is confirmed with no appeal.

The two sisters, who can appeal the verdict, were the subjects of a book written by Norwegian author Asne Seierstad.