ZURICH (Reuters) - Secret information on counter-terrorism shared by foreign governments may have been compromised by a massive data theft by a senior IT technician for the NDB, Switzerland'sintelligence service, European national security sources said.

Intelligence agencies in the United States and Britain are among those who were warned by Swiss authorities that their data could have been put in jeopardy, said one of the sources, who asked for anonymity when discussing sensitive information.