(Reuters) -Russia's defence ministry said on Wednesday that 89 servicemen were killed in the Ukrainian attack on Makiivka in the Moscow-controlled parts of the Donetsk region, adding the main reason for the attack was unauthorised use of mobile phones by the troops.
"It is already obvious that the main reason for what happened was the switching on and massive use - contrary to the prohibition - by personnel of mobile phones in a reach zone of enemy weapons," the ministry said in a statement.
"This factor allowed the enemy to track and determine the coordinates of the soldiers' location for a missile strike."
The strike just after midnight on New Year's Day on a school that was converted into military quarters in Makiivka has spurred anger among Russian nationalists and some lawmakers, questioning the military strategy used there. Russia previously said 63 Russian soldiers were killed.
The defence ministry said four rockets from the U.S.-made HIMARS launchers hit the building, adding that "from the detonation of the warheads of the HIMARS rockets, the ceilings of the building collapsed."
The ministry added in its statement on the Telegram messaging app that a commission is investigating the circumstances of the attack.
The ministry also suggested that in return, it launched air strikes launched at a "hardware concentration" near Druzhkivka railway station in Donetsk, killing up to 200 Ukrainian personnel, and destroying four HIMARS launchers and more than 800 rockets.
Reuters was not able to independently verify the report.
Kyrylo Tymoshenko, an aide to Ukrainian President Volodymyr Zelenskiy, said on Tuesday that two people were wounded in the attack on Druzhkivka, which destroyed an ice hockey arena.
(Reporting by Lidia Kelly and David Ljunggren; Writing by Lidia Kelly; editing by Grant McCool)