MINSK, Ukraine (AP) — Ukrainian authorities say they've thwarted a huge cyberattack and are blaming Russia for the alleged digital assault as tensions between the two countries have flared.

The Security Service of Ukraine said in a statement that hackers used malicious accounting documents to target the information technology systems of the country's judiciary.

The SBU described the alleged hacking as "massive" but produced little detail about the extent, timing, nature or severity of the hacks.

Ukraine has been buffeted by extraordinarily damaging cyberattacks since Russia annexed Crimea in 2014 and Russian-backed forces overran eastern Ukraine, leading to years of fighting.

The grinding conflict escalated on Nov. 25 when Russian forces fired on and seized three Ukrainian naval vessels carrying 24 seamen.

Russian government officials did not immediately return a message seeking comment Tuesday.