The toll from a Ukrainian New Year strike in Makiivka has risen to 89, Moscow said Wednesday, after Russians gathered to mourn the troops in a rare public display of anger and grief.

Russia said in the early hours of Wednesday that more bodies had been found under the rubble in the town of Makiivka in the Russian-controlled region of Donetsk and the toll had risen to 89.

The defence ministry declared that the tragedy had taken place because Russian troops had used cell phones, giving away their location to Ukrainian forces.

Russia said on Monday that 63 troops had been killed, the biggest loss of life from a single strike reported by Moscow since the start of the offensive in February.

"The number of our dead comrades has gone up to 89," Lieutenant General Sergei Sevryukov said in a video statement released by the defence ministry early Wednesday. More bodies had been found under the rubble, he added.

Ukraine struck a temporary base in Makiivka at 12:01 am local time on January 1, using US-supplied HIMARS rocket systems, Sevryukov said.

Russian President Vladimir Putin had just delivered his traditional New Year's address. The Kremlin chief hailed "our heroes" fighting in Ukraine and declared that "historical rightness is on our side."

Ukraine has taken responsibility for the strike and said the toll could be much higher. Russian war correspondents said many of the victims were reservists recently mobilised into the army.

The admission of the heavy losses came after the war correspondents, who have gained influence in recent months, accused Russia's top commanders of fatal incompetence.

Sevryukov said Wednesday that it was the use of cellphones by soldiers that had led to the deadly strike.

"Currently, a commission is working to investigate the circumstances of what has happened," he said.

"But it is already obvious that the main reason for what has happened was the turning on and massive use by personnel of mobile phones within reach of enemy weapons contrary to the ban."

He said measures were being taken to ensure such incidents would not happen in the future, and all those responsible will be punished.

The new announcement came after mourners gathered in several cities of the Volga region of Samara -- where some of the servicemen came from -- to mourn the dead.

- 'Grief unites' -

Some 200 people laid roses and wreaths in a central square in the city of Samara as an Orthodox priest recited a prayer.

Soldiers also fired a gun salute at the commemoration, where some of the mourners could be seen holding flags for the ruling United Russia party.

"It's very tough, it's scary. But we cannot be broken. Grief unites," Ekaterina Kolotovkina, head of a group of army spouses, said at the ceremony.

Similar gatherings were reported in other cities including Tolyatti, home to Russia's largest carmaker AvtoVAZ

Sevryukov also said that Russia had destroyed Ukraine's multiple launch rocket system used in the attack on Makiivka.

Russian strikes had also destroyed four more HIMARS launchers and killed 200 Ukrainian and foreign mercenaries in the town of Druzhkivka in the eastern region of Donetsk, he said.

Earlier in the day Ukrainian authorities said that Russian strikes on Druzhkivka killed one person and destroyed an ice rink.

The deaths sparked heavy criticism in Russia of the army's senior command, including from nationalist commentators favourable to the military intervention in Ukraine.

There have been reports that the servicemen were quartered in an unprotected building which was destroyed because munitions were stored on the premises and detonated in the strike.

Russian war correspondents have accused Russia's top commanders of not learning from past mistakes and seeking to shift the blame on the troops.

The Telegram account Rybar, which has around a million followers, said it was "criminally naive" for the army to store ammunition next to sleeping quarters.

But much of the criticism was focused on the incompetence of Russia's top brass and not President Vladimir Putin who sent troops to Ukraine on February 24 last year.

Putin has not yet reacted publicly to the Makiivka strike, which comes during a holiday season before Orthodox Christmas that many Russians spend with their families.

- Call for revenge -

At the gathering in Samara, Kolotovkina said she had asked her husband to "avenge" the victims.

"We will crush the enemy together. We are left with no choice," she told mourners.

A little-known group, dubbed Soldiers' Widows of Russia, urged Putin to announce general mobilisation.

Ukraine said it had faced waves of Russian drone and missile attacks since New Year's Eve, mainly targeting energy and other critical infrastructure.

On Tuesday, Ukrainian President Volodymyr Zelensky said he had spoken by phone with the leaders of Britain, Norway and the Netherlands and pointed to "the risks of escalation on the front".

The hardest fighting is raging around the city of Bakhmut in eastern Ukraine -- a location with little strategic importance that Russian forces led by the mercenary group Wagner have been trying to capture for months.