THE Russian army, seeking contract soldiers for what it calls the "special military operation" in Ukraine, is using mobile recruiting trucks to attract volunteers, offering nearly $3,000 a month as an incentive.

A special unit stationed one such truck in a central park in the southern Russian city of Rostov on Saturday and removed the sides to reveal a mobile office.

Soldiers in camouflage and black masks showed their guns to interested passersby and handed out colour brochures titled "Military service on a contract - the choice of a real man."

Neither Russia nor Ukraine disclose their military losses, which Western intelligence agencies estimate at tens of thousands on both sides.

Moscow has not updated the official death toll since March 25, when it said 1,351 Russian soldiers had been killed and 3,825 wounded. The Kremlin said last week there was no discussion of a nationwide mobilisation to bolster its forces. 

But the recruitment drive shows Moscow needs more men. The officer in charge of the Rostov truck said Russians and foreigners aged from 18 to 60 with at least a high school education would be eligible.

"Patriotically-minded citizens are choosing to sign contracts for three or six months to take part in the special military operation," major Sergei Ardashev said, promising training for everyone.

The minimum monthly wage on offer is 160,000 roubles ($2,700), which is almost three times the national average.

One potential recruit was musician Viktor Yakunin, who said he had always been attracted by the idea of military service and was now collecting necessary documents.

"I would love to serve in the airborne troops," he said. "My parents brought me up since childhood to love my homeland, to protect the Russian world. I believe the power is with us."

Inside the truck, Yakunin sat down with Ardashev, who told him the next step would be a mental examination. If he passed that, there would be physical test of speed, strength and endurance.

If all went well, Yakunin would "arrive at a military unit, enroll in a specific division, (and) from that moment you begin military service".

Outside young men, some with families, looked a temporary exhibition showing pictures of official heroes of the conflict, alongside a big sign that read "Tradition of victory".