The number of war criminals being discovered among asylum seekers in Sweden is rapidly increasing with the Swedish Migration Board claiming cases have doubled in the last two years.

In 2014, the Swedish Migration Board reported 12 asylum seekers to the Swedish police’s commission on war crimes but that number rose to 21 in 2015, 41 in 2016, and 52 last year, Svenska Dagbladet reports. Reports of suspected war crimes from other sources have also increased from 42 in 2015 to 79 in 2017.

Sweden convicted four war criminals in 2017, with one 48-year-old war criminal being found guilty of killing seven people in Syria. Investigations can be expensive to carry out and take years as they require the cooperation of foreign governments.

Patricia Rakic Arle, head of the war crimes commission, said: “A third of cases are related to incidents in Syria or Iraq, and besides those, there are scattered cases from other countries where there have been or are still conflicts.”

“We carry out many trips to interview plaintiffs. In an inquiry into a person’s involvement in the genocide of Rwanda, six, seven-day journeys are normally required. So far, the group has had three such investigations,” she added.

Security Service: Among Sweden's 'Refugees' Are Dozens Of Known Terrorists, Foreign Spies https://t.co/aWlepmLhSw pic.twitter.com/wj7DHLDkW6 — Breitbart London (@BreitbartLondon) March 11, 2016

In September of last year, the first member of the regime of Syrian President Bashar Assad to be convicted of war crimes was found guilty in Sweden. Mohammad Abdullah, who fled to Sweden as an asylum seeker, was sentenced to eight months in prison after he posted a photo of himself posing with his foot on a corpse.

Swedish prosecutor Henrik Attorps initially tried to have Abdullah brought up on murder charges but was unable to prove he had killed the individual he had posed with in the photograph.

“There is an international duty to act on these crimes,” Attorps said, and added: “Sweden should not be a safe haven for war criminals.”

Sweden has also noted a rise in violent Islamic extremists since the height of the migrant crisis in 2015. The Swedish security agency Säpo claimed last summer that there were 2,000 violent Islamic extremists in Sweden in 2017, compared to only 200 in 2010.