Suspected Russian hackers spied on U.S. Treasury emails - sources

FILE PHOTO: A hooded man holds a laptop computer as cyber code is projected on him in this illustration picture taken on May 13, 2017. REUTERS/Kacper Pempel/Illustration

WASHINGTON (Reuters) - Hackers believed to be working for Russia have been monitoring internal email traffic at the U.S. Treasury and Commerce departments, according to people familiar with the matter, adding they feared the hacks uncovered so far may be the tip of the iceberg.

The hack is so serious it led to a National Security Council meeting at the White House on Saturday, said one of the people familiar with the matter.