The proposal is expected to be officially presented by Swedish Home Affairs Minister Mikael Damberg at a meeting with his EU colleagues in Brussels on Thursday.
"There should be responsibility for human rights violations. If one commits a terrorist attack or war crimes, then there should be justice whenever [the offence] took place," Lofven said in an interview with Sweden's Aftonbladet news outlet.
The prime minister recalled that international ad hoc tribunals had been created earlier, but argued that the current situation had certain specificities.
"International tribunals have been created several times already, but, perhaps, this time it will not be possible to act in the same way," Lofven stated.
The future of the Daesh militants has recently come into the spotlight as the last pockets of terrorists are being cleared in Syria. The debate over the potential their return has especially intensified in Europe after on 16 February US President Donald Trump called on European countries to take back more than 800 Daesh fighters, captured by the United States in Syria, and put them on trial.
*Daesh — a terrorist group, banned in many countries, including Russia