Ukraine on Wednesday began calling up reservists into the armed forces and urged its citizens to leave Russia immediately as the pro-Western country braced for a possible invasion.

The call was issued a day after Russia's upper house of parliament gave President Vladimir Putin permission to send "peacekeepers" into two breakaway regions of eastern Ukraine.

Ukraine's armed forces said in a statement on Facebook that reservists between the ages of 18 and 60 would be called up for a period of up to one year.

Ukraine has a reserve force of more than 200,000 that is comprised mostly of military personnel who served in the first years of the country's eight-year war with Russian-backed separatists.

The decree signed by President Volodymyr Zelensky says former officers and non-commissioned personnel "will serve in military units and according to the specialisation" that they had in the past.

"If the reservist, for one reason or another prescribed by law, cannot be called up, they must personally present an explanatory document," it added.

"Failure to appear or disregard for the call-up can lead to administrative and criminal penalties," it warned.

The foreign ministry said the growing threat of Russian "aggression" meant that it would be increasingly difficult to provide consular services for Ukrainian citizens in Russia.

Between two and three million Ukrainians are believed to be living in Russia today.

"The foreign ministry urges the citizens of Ukraine to refrain from travel to Russia, and for those in that country to leave its territory immediately," the ministry said.

Ukraine's Foreign Minister Dmytro Kuleba also reaffirmed his call for world powers to stiffen their sanctions on Russia.

Western powers began to announce new penalties on Tuesday directed mostly against Russian banks.

"To stop Putin from further aggression, we call on partners to impose more sanctions on Russia now," Kuleba said in a tweet.

Ukraine defence minister warns of 'hardship', 'losses'
Kyiv (AFP) Feb 22, 2022 –

Ukraine's defence minister steeled his troops Tuesday to face "hardship" and human losses after Russia recognised two separatist regions and then ordered in troops to back up their independence claims.

Russian President Vladimir Putin on Monday recognised two rebel Ukrainian regions that have been fighting a deadly insurgency since 2014.

He then signed two decrees ordering Russian "peacekeepers" to support the regions' claims.

Ukrainian Defence Minister Oleksiy Reznikov posted an emotional message on his ministry's website telling his troops to be ready for war.

"There will be hardship. There will be losses. We will have to endure pain, overcome fear and despair," Reznikov said.

But he also promised "certain victory" in the face of the Russian threat.

"The Kremlin has taken another step to reviving the Soviet Union," Reznikov said.

"Yesterday, he showed his real face," he added, in reference to Putin.

"The face of a criminal who wants to hold the whole free world hostage."