Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: London (CNN) Tensions over Europe's migrant crisis led to arrests and violence in Sweden and the UK over the weekend, with a masked mob calling for attacks on foreigners in Stockholm and clashes between pro- and anti-migrant demonstrators in the British town of Dover. In Sweden, nearly 100 men gathered Friday night in the capital, handing out leaflets calling for attacks on migrants, Stockholm police spokesman Albin Naverberg told CNN. Some of the men were wearing black clothes and masks, he said. Reports of attacks on people from immigrant backgrounds surfaced in Swedish media and on social media, but police said they had received no reports of assaults on civilians.Mob hands out leaflets in Stockholm calling for assaults on migrants, police sayIn UK, pro- and anti-migrant protesters clash in DoverTensions rise as Europe faces largest migrant crisis in decades 
 Question:Friday's tensions were the latest in a series of incidents involving migrants in _.

Sweden