The soldier's face is caked in dust which leaves only his blue eyes just about visible. But he is alive in the ruined aftermath of a Russian military strike on a barracks at Mykolaiv which left dozens dead in the southern Ukrainian town.

A journalist at the scene heard sounds coming from within the debris and called rescuers, who shifted piles of rubble with their bare hands for an hour before managing to extricate the man.

Despite being in shock, he tried gamely to speak with the stretcher bearers as they carried him away.

Witnesses to the attack told AFP that six rockets hit the site, which originally had served as a young officers' academy, around six o'clock in the morning on Friday.

"An enormous explosion," says one resident, Nikolai. The blast reduced to rubble several buildings in the district.

"No less than 200 soldiers were sleeping in the barracks," says Maxim, 22, who had been stationed nearby and looks on aghast at the scale of the destruction.

"At least 50 bodies have been pulled out but we don't know how many remain under the debris," he says.

Another soldier, Yevgeny, says as many as 100 people could have been killed, in an attack with no official toll to date and details of which remain hazy.

Ukrainian authorities say only that Mykolaiv, which they describe as being a "shield" to the key strategic military port of Odessa, some 130 kilometres (85 miles) further west, is resisting Russian attacks and pushing back the invaders' assaults.

Kyiv authorities have been saying for several days that Russian forces have been pushed back towards Kherson, another southern town further to the east and under Russian control.

Regardless, Russian strikes which have been hitting civilian targets as well as military facilities for the past fortnight, continue to be relentless.

- Mangled bodies -"We aren't allowed to say anything because the rescue operation isn't over and the families haven't all been informed," military spokeswoman Olga Malarchuk says, first in Ukrainian before switching to Russian.

Visibly moved, she continues: "We are not yet able to announce a toll and I cannot tell you how many soldiers were present."

Ukraine's presidency is not answering questions about the bombing.

"Yesterday orcs hit our sleeping soldiers with a rocket in a cowardly manner," Vitaly Kim, head of the regional administration, said in a video, using the Ukrainian nickname for Russian forces.

He added that he was awaiting official information from the armed forces.

Rescuers and firefighters have been relentlessly working at the razed site since Friday, accompanied by the throbbing sound of an excavator clearing the enormous heap of stones, concrete and twisted metal rods.

An arm covered in blood and a piece of human torso are laid on a tarpaulin by the rescuers.

Further on, three bodies, including one covered in a white sheet, have been moved away from the rubble.

The victims' military bags and bulletproof vests lay gathered together in the corner.

A few metres from the destroyed barrack, another, less damaged building still houses a dormitory and some offices.

All the windows have been blown out but a small painting of a religious icon as well as photos of soldiers are still hanging on the wall.

A grey stone statue, depicting a sailor leaning on a gun, ships in the background, remains standing amid the scene of desolation.

Probably destined to have been placed at the entrance of the bombed barracks, a poem is visible on it.

Its first words read: "Fight! You'll win".