A view shows the Third Vishnevskiy Central Military Clinical Hospital in Krasnogorsk, Russia February 16, 2018. REUTERS/Sergei Karpukhin

KEDROVOYE, Russia (Reuters) - The mother of a Russian man who is believed to working as a military contractor in Syria said on Friday the Kremlin had abandoned her son and those fighting alongside him.

Around 300 men working for a Kremlin-linked private military contractor were killed or injured in Syria last week, sources told Reuters, indicating Russia is more deeply involved in Syria’s war than it has previously said.

Russian officials say only five civilians may have been killed and a spokesman for President Vladimir Putin has said the Kremlin has no information about any casualties.

Valentina Berdysheva said her oldest son, Alexander Potapov, and five other men left to fight in Syria as military contractors in October. At least one of them has since died, she said, and the whereabouts of her son are unknown.

“They are there illegally, the government has disowned them, even Putin says our soldiers are not there,” Berdysheva, 80, told Reuters.

She said her son previously fought in two wars in Russia’s Chechnya region but later struggled to find work in their village.

The group of men including her son told friends they had found “a gig” before travelling to the southern Russian city of Rostov-on-Don, she said, and she later heard he was working in Syria.

“Who will help us? They left on their own, somebody came there to collect them and took them away. Where did they go?”