Unauthorised use of mobile phones by Russian soldiers led to a deadly Ukrainian rocket attack on the facility where they were stationed, the Russian military said late Tuesday, raising the death toll from the weekend attack to 89.

Gen. Lt. Sergei Sevryukov said in a statement that phone signals allowed Kyiv’s forces to “determine the coordinates of the location of military personnel” and launch a strike. Sevryukov said unspecified measures were being taken to “prevent similar tragic incidents in the future” and promised to punish officials responsible for the infraction.