Ukraine's top mobile operator hit by biggest cyber attack of war so far

FILE PHOTO: The headquarters of Kyivstar, one of Ukraine's largest telecoms company, is seen in Kiev, Ukraine, March 3, 2016. REUTERS/Gleb Garanich/File Photo

KYIV (Reuters) - Ukraine's biggest mobile network operator was hit on Tuesday by what appeared to be the largest cyber attack of the war with Russia so far, knocking out mobile and internet services for millions and the air raid alert system in parts of Kyiv region.

Kyivstar has 24.3 million mobile subscribers - more than half of Ukraine's population - as well as over 1.1 million home internet subscribers.