BERLIN (Reuters) - NATO may react to future cyber attacks by deploying conventional weapons, NATO Secretary-General Jens Stoltenberg said in an interview published by Germany's Bild newspaper on Thursday.

"A severe cyber attack may be classified as a case for the alliance. Then NATO can and must react," the newspaper quoted Stoltenberg as saying. "How, that will depend on the severity of the attack."

The NATO chief told the newspaper that the alliance needed to adjust to the increasingly complex series of threats it faces, which is why NATO members have agreed to defend against attacks in cyberspace just as they do against attacks launched against targets on land, in the air and at sea.

NATO members are expected to agree at their upcoming summit in Warsaw to designate cyber as an official operational domain of warfare, along with air, sea, land and space.

Individual members have already made similar announcements, including the United States, which said in 2011 that it would respond to hostile attacks in cyberspace as it would to any other threat.

(Reporting by Andrea Shalal; Editing by Dan Grebler)