Reports from the United Kingdom say a Swedish national was detained after arriving in London on suspicion of terror related crimes.
The woman was arrested shortly after arriving from Italy at the Gatwick airport on Thursday.
Authorities in Sweden could not immediately comment or confirm.
Sofia Hellqvist, a press officer at Swedish security service Säpo, referred the media requests to the Foreign Ministry who are responsible for dealing with Swedes arrested overseas.
The suspect, reports say, remains in police custody and is suspected of Islamic extremism, including commission, preparation or instigation of acts of terrorism.