As the doctor prepared to administer an injection, the loud thud of an artillery shell in the distance broke the silence in the operating room.

The staff at this emergency medical treatment point for soldiers near the Zaporizhzhia frontline in Ukraine's south, aren't fazed by the danger.

"We don't have time to think things over or have doubts, we don't have time to worry, because this is our job and we have to do it," said Denys, a 35-year-old surgeon who had just finished stitching up a soldier's head wound as the blasts thudded.

There have been near misses. In March, a Russian rocket landed 10 metres from the old, single-storeyed building's entrance, showering shards of glass and chunks of brick onto rudimentary operating tables. Less than two weeks ago, another rocket flattened a chunk of a nearby schoolhouse.

Denys, who like most other staff would give only a first name, runs the centre, known as a stabilisation point. Similar stations are found within easy reach of all Ukrainian frontlines.

The job of the medics here is to perform emergency first aid on casualties so they survive the journey to hospitals further from the fighting - a task expected to become even more vital when Ukraine launches its long-awaited counteroffensive.

Ukraine has shrouded figures about its wartime casualties in secrecy. The doctors would not say how many they treat or whether the number has changed over time.

The biggest danger to Ukrainian soldiers, like the shaven-headed serviceman with flecks of blood glistening on his forehead where Denys had stitched up his head wound, is from Russia's artillery.

The soldier, who had been thrown to the ground by the blast wave from a shell, would now be sent to a hospital to be examined for possible brain injury.

Ihor, a doctor with 15 years of experience as an army medic, said artillery accounted for about 90% of injuries he had dealt with since the full-scale invasion began in early 2022.

He appeared weary, but said he was ready for the long haul.

"Most of those who were mobilised thought this would end quickly ... but those of us who were in the army for a long time understood that this won't just last a month or two, but a long time."

It was toughest when several casualties arrived at once, knowing it would not be possible to treat everyone immediately, said another doctor, also called Ihor.

"Understanding who needs to be given aid, who unfortunately can no longer be given aid, who can wait for aid: its hard to get used to these things."

Much of the equipment in the stabilisation point has been provided by private and NGO donations from Ukraine and abroad.

Doctors were particularly proud of a state-of-the-art Canadian machine worth over $160,000 which can supply oxygen, provide artificial lung ventilation and monitor patients.

Vitaliy, a 30-year-old anaesthesiologist demonstrating the machine, said the frontline doctors sent regular feedback to its Canadian manufacturer, to shape an assessment of its effectiveness in combat situations. (Reporting by Max Hunder Editing by Peter Graff)