Vladimir Putin has said any foreign nationals who fight for him in Ukraine will be offered Russian citizenship for them and their families.
He issued the decree on Thursday, saying it applied to people who have signed contracts during what Moscow calls its "special military operation" in Ukraine.
They can apply to get Russian passports for themselves and their spouses, children and parents.
They must provide documents showing that they signed up for a minimum of one year.
Those eligible include people who have signed contracts with the regular armed forces or other "military formations" - a description that could apply to groups such as the Wagner mercenary organisation.
The measure appeared to be aimed at creating additional incentives for foreigners with military experience to apply to join Russian ranks.
Moscow does not publish data on the number of foreigners fighting on its side in Ukraine but there have been several reports of it happening.
Reuters previously revealed how Cubans signed up for the military in return for bonuses equivalent to more than 100 times the average Cuban monthly salary.
At least three Africans are known to have been recruited by Wagner, two of whom were killed in action.
A declassified US intelligence report assessed that the Ukraine war has cost Russia 315,000 dead and wounded troops.
This is close to 90% of the personnel it had when the conflict began, according to a source familiar with the intelligence.
Russia drafted an extra 300,000 men in September 2022, in its first mobilisation since World War Two.
There has been persistent speculation it could repeat the unpopular move, perhaps after the next presidential election in March in which Putin is set to stroll to a new six-year term.
The Kremlin has repeatedly said no further mobilisation is needed, however, because hundreds of thousands of men signed voluntary contracts last year to become professional soldiers.
Neither Moscow nor Kyiv has disclosed the extent of their losses in Putin's 22-month war on Russia's neighbour.
Ukrainian President Volodymyr Zelensky said last month that his military had proposed mobilising 450,000-500,000 more people, and the Kyiv parliament on Thursday began reviewing a contested piece of draft legislation that would tighten and expand mobilisation rules.
