Russia’s president has signed a decree which could see 137,000 service personnel added to the country’s armed forces in the coming months.
Currently Russia has a limit of just over a million military personnel and almost 900,000 civilian staff.
Vladimir Putin’s decree comes amid a recruitment drive around the country, with large cash incentives on offer.
Western officials say 70-80,000 troops have been killed or wounded since Russia invaded Ukraine six months ago.
There have been reports that recruiters have even been visiting prisons, promising inmates freedom and money.
The UK Ministry of Defence said in a statement two weeks ago that volunteer battalions being set up in several Russian regions were likely to form part of a new army corps.
But it said “very limited levels of popular enthusiasm for volunteering for combat in Ukraine” meant it would be difficult to find the required number of troops.
Russia had initially promised a short, decisive campaign when it invaded Ukraine in February, but fierce Ukrainian resistance has stalled its progress and in recent weeks front lines have hardly moved.