Spanish media report that the man was seized on Friday in the Sants-Montjuïc area of Barcelona when he targeted a woman who managed to scream for help. When other people arrived the man is said to have fled on foot, but two people ran after him, caught him and held him until police arrived.
The man, who lives in Sweden's western Götaland region, is understood to have been in Barcelona as a tourist and is now suspected of sexually assaulting four different women. He is said to have grabbed hold of them from behind, covered their mouths and touched them inappropriately, reports Aftonbladet.
Sweden's foreign ministry confirms that a Swedish man in his mid-20s is in custody in Spain.
"We are in contact with the embassy in Madrid. We have no more updates for now," foreign ministry spokesperson Johanna Westlund told the TT news agency.