Men and women aged from 18 to 60 years old can be called up as reservists.
Following President Vladimir Putin's "partial mobilisation" order last week, the US Embassy in Moscow has urged all Americans living in Russia to leave the country while there are still possibilities to do so.
The American embassy issued a warning that things are already extremely challenging in Russia. With crowded border checkpoints and few commercial planes available in the wake of the war, leaving the country is becoming increasingly more difficult.
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"Russia may refuse to acknowledge dual nationals' U.S. citizenship, deny their access to U.S. consular assistance, prevent their departure from Russia, and conscript dual nationals for military service.Those residing or traveling in Russia should depart Russia immediately while limited commercial travel options remain," the statement released by the embassy said.
"Russia may refuse to acknowledge dual nationals' US citizenship, deny their access to US consular assistance, prevent their departure from Russia, and conscript dual nationals for military service," the embassy warned.
Since the Russian President ordered the partial mobilisation of 300,000 soldiers in Ukraine, thousands of individuals who are eligible for conscription have tried to leave the country.
Images that have appeared online show that hundreds of people are crammed into Russian airports, and that thousands of cars have blocked Russian highways.
The vast exodus from Russia has seen thousands of military-age men make for the borders with Finland, Georgia, Kazakhstan and Mongolia.
Kazakhstan's Interior Ministry on Tuesday said that 98,000 Russians had entered the country in the last week, although 64,000 had left. The ministry said it would not repatriate Russians who entered the country in order to dodge the draft.
Russians can stay in Kazakhstan for up to 90 days without a visa.
What does Vladimir Putin's 'partial' mobilisation mean for Russia's military machine?
President Vladimir Putin on September 21 ordered Russia's first mobilisation since World War Two after suffering a major battlefield reversal in Ukraine, in an attempt to turn the military tide in what he has cast as a defining East-West clash.
The mobilisation is, for now, being officially described as a partial one that will steadily draw in 300,000 reservists from across the world's largest country over a period of months, rather than a full call-up that would rely on what Russia's defence minister says is a vast reserve force of 25 million people.
Men and women aged from 18 to 60 years old can theoretically be called up as reservists according to Russian legislation, depending on their rank.
Western military analysts have long said that Russia is suffering serious manpower shortages on the Ukraine battlefield due to heavy losses, while Russian nationalists have for months been calling for some kind of mobilisation to inject new life into what they have described as a stuttering campaign.
The military is looking for reservists who have done specific and specialised jobs in the army in the past, such as tank drivers, sappers and snipers. However, the exact list of specialities it requires is classified as that would reveal where Russia has personnel gaps.
Professional soldiers known as 'kontraktniki' who are currently serving in the armed forces will have their contracts automatically extended until the authorities decide to end the period of temporary mobilisation. In other words, it just became much harder for serving professional soldiers to quit.
(With inputs from Reuters)