The White House is calling on Europe to take "proactive action" to disrupt the Hezbollah organization following an investigation that tied the group to the bombing of a bus filled with Israeli tourists in Bulgaria last year.

White House counterterrorism adviser John Brennan says Europe, as well as other international partners, must seek to uncover Hezbollah's infrastructure and disrupt the group's finances and operational network in order to prevent future attacks. Brennan is President Barack Obama's nominee to run the Central Intelligence Agency.

Investigators on Tuesday implicated Hezbollah in the bombing last July, which killed five Israelis and their Bulgarian driver. Brennan commended Bulgaria for its comprehensive investigation and says the U.S. will provide the Bulgarian government assistance in bringing the perpetrators of the attack to justice.