Ukraine's deadliest day: The battle of Ilovaisk, August 2014

It was the biggest loss of life in Ukraine's war against Russian-backed separatists.

Hundreds of soldiers died as the Ukrainian army and volunteers retreated in a column from the eastern town of Ilovaisk on 29 August 2014.

Ukrainian veterans are adamant the Russian army was there, even though Moscow has always denied claims that regular Russian forces took part in the battle.

President Vladimir Putin has said merely that any Russians involved were volunteers following "a call of the heart".

How the battle was lost

At first it seemed like any other operation against Russian-backed separatists, says Roman Zinenko, 45, a former soldier who served in the Dnipro-1 volunteer police battalion that fought in the battle of Ilovaisk.

Image copyrightUKRINFORM

Image captionFighting had already been intense around Ilovaisk, and the Ukrainian forces thought the battle was over

The Ukrainian army had surrounded the town and their battalion had been ordered to "wipe out" the Russian-backed force.

But on 24 August, Ukraine's independence day, they began receiving calls from relatives.

Ilovaisk was surrounded, Ukrainian media were reporting.

"We did not feel that, because the [Ukrainian] army held positions around the city," he told the BBC. "On August 24, we even captured the enemy's fortified area."

But the next day, heavy mortar shelling began and the school they were using as a base was raided.

Image copyrightROMAN ZINENKO

Image captionUkrainian forces had initially surrounded Ilovaisk but then they themselves became trapped

"We realised the enemy had reinforcements," he says.

"At the time we could not imagine the scale of this entrapment. Our troops had surrounded Ilovaisk but all our troops were surrounded by the enemy".

Negotiations were going on and a humanitarian corridor was being prepared for them to leave, they were told, and yet their withdrawal was repeatedly postponed.

How soldiers became trapped in 'bloody corridor'

Then, on the morning of 29 August 2014, came the command to gather and leave Ilovaisk in two columns.

"Nobody knew the routes," said Roman Zinenko.

They began to move, they passed the first ring of encirclement smoothly but within a few kilometres their column came under fire.

"It was just a shooting range and we were the targets," he said.

Roman and his fellow soldiers had set out in a security van because of a lack of equipment. But its wheels and motor were shot up so they switched to a light-armoured vehicle and kept going under constant fire.

Behind them, an infantry fighting vehicle carrying more than 10 soldiers was hit by a shell.

Bodies were thrown everywhere by the force of the blast.

"I can still see it. This body flying high, turning in the air and ending up hanging from a power line."

Image copyrightROMAN ZINENKO/OLEXIY RUBETS

Image captionRoman Zinenko (left) with commander Denys Tomilovych, who died in the retreat from Ilovaisk

They drove on a few more kilometres until their vehicle was disabled.

He escaped unharmed but his commander, Denys Tomilovych, was hit in the head by a 30mm automatic cannon shell.

"Another fighter sat next to him, he was injured too," said Roman Zinenko. "When Den was hit in the head, fragments of his helmet and skull just cut his forearm."

Roman and his comrades managed to survive and escaped the encirclement two days later.

Image captionSurvivor Roman Zinenko remembers the victims of the battle of Ilovaisk

According to official Ukrainian data, 366 Ukrainian soldiers were killed in the Ilovaisk battle.

The true figure may be at least 400, when you include soldiers registered missing or unidentified by their relatives.