The Islamic State group on Monday claimed responsibility for the New Year's attack at a popular Istanbul nightclub that killed 39 people and wounded scores of others.

The Tunisian man sought as the primary suspect in connection with the truck attack on a Berlin Christmas market this week was killed early Friday morning by Italian police near Milan, Italy.

France is reeling from another large-scale terror attack. This time it was on Bastille Day, the national holiday that celebrates democracy -- a value at the very heart of French society. 

Attacks Tuesday on the Brussels airport and its subway system have led authorities in Europe and elsewhere to tighten security at airports, on subways, at the borders and on city streets