Dozens of Russian soldiers are facing trial for fleeing their unit, fearing deployment to Ukraine, a news site and a lawyer for five of the men said Saturday.

The popular Gazeta.ru website said several dozen soldiers would be prosecuted after fleeing a training ground in southern Russia where they were under pressure to "volunteer" to fight in Ukraine.

The troops had freely enlisted for the army and are not draftees, it said.

It is the latest report to allege Russian soldiers are being sent to eastern Ukraine despite Moscow's insistence that only "volunteers" are fighting alongside the pro-Russian separatists.

The defence ministry said that only four soldiers named in the report are under investigation for "disciplinary offences", denying dozens were involved, the Echo of Moscow radio station reported.

Gazeta.ru cited mothers of two soldiers from the unit, based in the town of Maikop in the North Caucasus, as saying their sons had fled a training ground in the southern Rostov region, fearing being sent to Ukraine.

- Pressure to 'volunteer' -

A lawyer representing five of the soldiers, Tatiana Chernetskaya, speaking by phone to AFP confirmed the report and said "dozens" of soldiers faced tribunals.

"They all have the same story. They all served together in the same unit," said Chernetskaya, based in the southern town of Krasnodar.

"They weren't directly forced to go to Ukraine. People came to the unit to canvass them to go," Chernetskaya said, adding the recruiters were "not wearing any identification tags."

"According to the soldiers, they offered 8,000 rubles ($142) per day," she said.

The soldiers fled, not wanting "to find themselves in battle," she said.

Since Russia is technically not at war with Ukraine, "if they were sent to Ukraine, it could be seen as a criminal act," she added, calling the soldiers "law-abiding."

"They went back to Maikop and started writing resignation letters but these were not accepted and this all led to the launching of criminal cases."

She said four of her clients are charged with going AWOL while one is charged with the more serious offence of desertion.

She said soldiers started going on trial in March and several had already been convicted.

Gazeta.ru cited the mother of 21-year-old soldier Ivan Shevkunov, who is facing up to 10 years' jail as a deserter.

"He said that soldiers were being forced to go (to Ukraine) as volunteers," said the soldier's mother, named as Svetlana Nikolayevna.

Gazeta.ru also published a handwritten statement by another soldier, Pavel Tynchenko, who has been charged with going absent without leave.

In the statement to the judge of the military tribunal, Tynchenko wrote: "I did not want to go against the oath I swore and did not want to take part in military actions in Ukraine."

Gazeta.ru cited official statistics on Maikop garrison's military tribunal, saying it convicted 62 soldiers of going AWOL in the first half of 2015.

The court's website says a soldier from the Maikop unit on Thursday was convicted of going AWOL and robbery and sentenced to nine months in a prison colony.

The Kremlin's rights council, an advisory body, is due to visit Maikop next week and Chernetskaya said she planned to meet them to raise the soldiers' trials.

"The number of witnesses of this state crime (illegally sending soldiers to participate in an undeclared war) is already such that it is impossible to conceal them," opposition politician Alexei Navalny wrote on his blog.