Russian President Vladimir Putin signed a decree Wednesday to expedite the applications from some Ukrainians living in areas held by Russia-backed separatists in under three months. Those granted Russian citizenship would have to swear allegiance to Russia.
In a joint statement, France and Germany - European guarantors of the 2015 Minsk peace accord - said the decree "goes against the spirit and aims of the Minsk agreement."
More than 13,000 people have been killed in fighting between Ukrainian troops and Russian-backed separatists in eastern Ukraine.
"This is the opposite of the urgently necessary contribution toward de-escalation," the German foreign ministry said.
European Commission spokeswoman Maja Kocijancic said "we expect Russia to refrain from actions that are against the Minsk agreements and impede the full reintegration of the non-government controlled areas into Ukraine."
She described the move as "another attack on Ukraine's sovereignty by Russia."
The EU imposed sanctions on Russia in 2014 after it annexed Ukraine's Crimean Peninsula and has continued to prolong the punitive measures over what it maintains is Moscow's foot-dragging in respecting the Minsk peace agreement.
The new decree was signed just days after the presidential election in Ukraine, and Kocijancic said this "shows Russia's intention to further destabilize Ukraine and to exacerbate the conflict."
Volodymyr Zelenskiy, a TV star with no political experience who won a landslide victory in Ukraine's presidential runoff vote polls Sunday, said Russia's move confirms its role as an "aggressor state" in the conflict in eastern Ukraine.
Putin defended his decision on Thursday, saying it would help people stranded in areas where Ukrainian government services are not available.
Frank Jordans in Berlin and Nataliya Vasilyeva in Moscow contributed to this report.
Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.