A man captured in Afghanistan has tipped off investigators to a potential "Mumbai-style" terror plot in Europe, a German counterterror source said Wednesday.
Investigators believe Osama bin Laden signed off on a European attack plan, a separate law-enforcement source said.
The potential plot is one reason for a dramatic increase in the number of missile strikes by unmanned drones against terrorist targets in Pakistan, according to a U.S. official.
The number of suspected U.S. drone strikes in Pakistan jumped to 20 this month - more than in any previous month and twice the monthly average, according to a CNN estimate based on information from Pakistani officials.
A federal law enforcement official in the United States, meanwhile, said "the volume seems to be turned up" on the threat information coming out of Europe.