AMSTERDAM (AP) — The Netherlands' spy service broke into the computers used by a powerful Russian hacking group and may be sitting on evidence relating to the breach of the U.S. Democratic National Committee, a Dutch newspaper and television show jointly reported Friday.

Reports carried in the respected daily Volkskrant and by the current affairs show Nieuwsuur said hackers working for the Dutch General Intelligence and Security Service penetrated the computers used by the group, often nicknamed Cozy Bear, in mid-2014 and watched them for at least a year, even managing to catch the hackers on...