Up until now, the government always announced beforehand where and when it sends its test alert messages to people. On Sunday, however, an unannounced version was sent to simulate a real emergency situation.
Violence broke out in Brussels on Sunday after Morocco beat Belgium in the World Cup, with "dozens of people" attacking street furniture and police, police said.
Aside from the physical altercation in Mersch, police also had to respond to a drunk disturber at the winter market in Strassen.
At least five burglaries occurred across Luxembourg between Saturday and Sunday.