An outpouring of support from militant Islamist groups for Hamas’s bloody incursion into Israel is stirring fears of a resurgence of terrorist acts in the West that, until recently, appeared to be on the decline.

U.S.-designated terrorist groups from Africa to Pakistan have praised the Hamas attack earlier this month. Officials already see stirrings of violence in Europe, where on Monday a man claiming affiliation to Islamic State shot to death two Swedes in Brussels. FBI Director Christopher Wray has warned of the possibility of copycat attacks on U.S. soil, as has his counterpart in the U.K.